Religion: Spreading and Defending Your Religion (G&K)

Introduction

A religious war roils beneath the surface of every game, as you and your rival leaders seek to extend your religions to heathen lands. The benefits of most founder beliefs are greatly enhanced if you spread your religion beyond your own culture borders, and most enhancer beliefs will facilitate that spread and/or help you defend against the efforts of other religions to spread among your followers. This article describes how to spread and defend your religion:

• Key concepts
• Why should I spread my religion?
• How does religion spread?
  • How does pressure work?
  • Mechanics of manually spreading your religion
  • Missionary or Great Prophet?
  • What enhancer beliefs will best help me spread my religion?
• How do I defend my religion?
  • How do Inquisitors work?
  • How do I deal with pressure?
  • How can enhancer beliefs help me defend my religion?
• Conclusion

Other articles in this series provide an overview of the religion system (including what faith is, how to generate faith and how to found a pantheon), how to found and enhance your religion, and detailed reviews of the many available pantheon, founder, follower and enhancer beliefs.

Why should I spread my religion?

Spreading your religion allows you to gain the most benefit from your chosen founder beliefs, provides modest diplomatic benefits when other civilizations adopt your religion, and reduces by 25% the rate of City State influence decay in CSs that have adopted your religion (which stacks with the 25% reduction from the Patronage opener for a 50% reduction). Having made the decision to found a religion, it is in your interest to make the most of that investment.

There are 9 founder beliefs, providing happiness, gold, science, faith, culture or CS influence (for detailed information about founder beliefs and how they can facilitate various strategies, see "Founder Beliefs"). Of the 9 founder beliefs, only 4 provide benefits from spreading your religion to your own cities, as well as to City States and other civilizations:

• Ceremonial Burial: +1 for each City following this religion
• Church Property: +2 for each City following this religion
• Initiation Rites: +100 when each City first converts to this religion
• Tithe: +1 for every 4 followers of this religion

The benefits of 4 other founder beliefs depend solely on your ability to spread your religion to other civilizations:

• Interfaith Dialogue: Gain Science when a Missionary or Great Prophet spreads this religion to cities of other religions
• Peace Loving: +1 for every 5 followers of this religion in non-enemy foreign cities
• Pilgrimage: +2 for each foreign city following this religion
• World Church: +1 for every 5 followers of this religion in other civilizations

Finally, the benefits of Papal Primacy depend entirely on your ability to spread your religion to City States.

How does religion spread?

Your religion will automatically appear in the city in which you found your religion (typically your capital, but you can relocate your first Great Prophet to another city and found your religion there, if you prefer). Unlike your pantheon, your religion will not automatically appear in your other cities. You must spread your religion to your other cities and to cities of other civilizations and to City States. There are two ways to spread religion to other cities:

• Passive spread through religious pressure
  
• Manual spread through use of Great Prophets and Missionaries

How does pressure work?

Each city with a majority religion exerts religious “pressure” on neighboring cities. Once pressure reaches certain levels, a citizen of a neighboring city will convert to that religion (become a “follower”). Once the followers of a religion are a majority of that city’s population, that city will also start exerting religious pressure on its neighboring cities, potentially triggering a cascade (or snowball) effect as neighboring cities experience pressure from multiple cities.

Religious pressure is a reciprocal concept, in that each city with a religious majority will exert pressure on its neighbors while at the same time it will experience pressure exerted on it by those its neighbors that have a majority religion (either the same religion or a different religion). The amount of pressure exerted by a city on its neighbors does not depend on that city's population or the presence or absence of religious buildings (with one exception--the Grand Temple--described below). A 1-pop city with 1 follower and no religious buildings exerts as much pressure on its neighbors as a 30-pop city with 28 followers and a shrine, temple, cathedral and pagoda. You can determine the pressure experienced by a given city by hovering your mouse over the city banner.

By default and at Standard speed, each city exerts 6 pressure on other cities located within 10 tiles. So, if there are 4 cities of your religion within 10 tiles of a given city (the "target" city), the target city will be experiencing 24 (6 x 4) pressure. In the image to the right, because Dur-Kurigalzu is located within 10 tiles of two cities following Christianity and two cities following Buddhism, it is experiencing 12 pressure from each religion. At the same time, Dur-Kurigalzu is exerting 6 pressure on each of those cities, as well as any other cities within 10 tiles that do not have a majority religion.

The Itinerant Preachers enhancer belief extends the effect of pressure to 13 tiles, while the Religious Texts enhancer belief will result in 8 pressure (and later 10 pressure, after Printing Press is researched). Because both of these enhancer beliefs facilitate religious spread, they are popular with both human players and the AI.

Each Holy City exerts a special type of “internal” pressure that is intended to help it maintain its Holy City status. That internal pressure is only experienced by the Holy City, and not neighboring cities. Accordingly, a Holy City generally exerts the same pressure on neighboring cities as other cities do. But, if the Holy City has the Grand Temple, the Holy City’s external pressure on neighboring cities is doubled (e.g., from 6 pressure to 12 pressure).

Mechanics of manually spreading your religion

Each Great Prophet can spread your religion 4 times and each Missionary can spread your religion 2 times (and one additional spread for each, if the Great Prophet or Missionary is purchased in the city that has the Great Mosque of Djenne). To spread to another city, your Great Prophet or Missionary must be immediately adjacent to your target city’s center tile. When you are adjacent to the target city's center tile, you can see how many citizens of that city will be converted. As the image to the right shows, the Celtic Missionary can convert 5 of the 8 citizens of the puppeted Hunnic capital.

Missionaries get 4 movement points, while Great Prophets only have 2 movement points, but both are hampered by terrain movement penalties. And, since both are civilian units, they cannot pass through, and must go around, any other civilization's units (civilian or military). Accordingly, their movement can be passively blocked by a wall of units, preventing access to the intended target of their conversion efforts.

Great Prophets can cross any culture borders without penalty and without the permission of the civilization that owns those tiles. Missionaries, on the other hand, have the "unwelcome evangelist" penalty and must have Open Borders to enter another civilization's culture borders (but not City States) or risk suffering attrition. If a Missionary spends a turn inside the culture borders of a civilization with whom you do not have an open borders treaty, it will lose 250 of its conversion strength through "attrition". Passing entirely through culture borders during a turn doesn't result in attrition, and attrition doesn't happen on the turn you use the missionary to spread, so you can avoid attrition if you depart promptly.

Losing Missionary conversion strength has two consequences: (1) a weakened Missionary will convert fewer followers when the Missionary is expended and (2) the Missionary will die if it experiences attrition that takes its conversion strength to 0. A Missionary with 1000 conversion strength can endure 3 turns of attrition (and will die on the 4th), while one with 25% additional conversion strength from the Missionary Zeal enhancer belief should survive 4 rounds of attrition.

Attrition is distinct from garden-variety health/hit points. Missionaries do not have combat strength to speak of but can occasionally survive ranged attacks and will "heal" in the regular way in friendly territory. But attrition is not heal-able; if you are inattentive to your Missionary's stopping point on a given turn, and attrition happens, there is no way to restore the Missionary's conversion strength.

Missionary or Great Prophet?

Many players choose to enhance their religions as quickly as possible, to avoid losing their preferred enhancer belief, and commence manual spread of their religion after enhancement. Others prefer to get their religion’s spread started early by buying a Missionary in their holy city before enhancing their religion, and use the Missionary to spread their religion to two nearby cities. This delays enhancement of their religion (requiring faith be re-accumulated to the 300 level to generate another Great Prophet), but may trigger a beneficial cascade of religion adoptions by surrounding cities as a result of religious pressure. Whenever you commence your spread, you generally should try to convert two nearby cities with more substantial populations (often City States), rather than your own recently founded, low-population cities; the mechanics of religious pressure dictate that low population cities will adopt your religion more quickly than larger population City States.

On other occasions during the game, you may find it advantageous to use additional Missionaries and Great Prophets to convert more cities, which leads to the question: when should I use a Missionary and when should I use a Great Prophet?

It should be no surprise that the answer requires a form of cost-benefit analysis:

• Missionaries are substantially weaker than Great Prophets, even where they have the same nominal conversion strength of 1,000. First, Missionaries are able to perform 2 fewer conversions than Great Prophets, which directly affects Missionaries' "value proposition." Also, when a Great Prophet spreads its religion, it eliminates all other religions from the target city at the same time it converts a number of citizens to become followers of its religion. Missionaries, on the other hand, must try to convert existing followers of other religions, which is substantially more difficult. Accordingly, Missionaries are most effective in spreading their religion to cities that do not already have an entrenched religion, while Great Prophets are more effective later in the game, when many cities have large numbers of followers of other religions.
  
  
• On a faith-cost-per-conversion basis, Missionaries can be less expensive (in terms of faith) than Great Prophets, depending on the era. For example, assuming you used your first two Great Prophets to found and enhance your religion, your next Great Prophet will be randomly generated after you cross the 500 faith level and the next Great Prophet after you cross the 800 faith level. Since a Great Prophet will be able to spread your religion 4 times, the 500-faith Great Prophet has a faith-cost-per-conversion of approximately 125 faith, while the 800-faith Great Prophet has a faith-cost-per-conversion of approximately 200 faith. In contrast, in the Medieval Era, a Missionary would cost 200 faith, or faith-cost-per-conversion of 100 faith. Since Missionaries' effectiveness is greatest early in the game, when few cities have religions, it can be advantageous to use faith to buy Medieval Era and and Renaissance Era (300 faith) Missionaries to convert nearby cities, and preserve your ability to generate Great Prophets for 500 and 800 faith in later Eras. As you enter each Era, your Missionary cost will rise by 100 faith per era, while your Great Prophet costs will remain on their own "counter" (200, 300, 500, 800, 1200, etc. faith). By the Modern Era, when Missionaries cost 500 faith, you may be relying almost exclusively on Great Prophets to continue spreading your religion, in light of relative faith costs and spread effectiveness.

One important caveat to this analysis is where you have selected the Interfaith Dialogue founder belief, which provides science when a Missionary or Great Prophet spreads your religion to cities of other religions--essentially transforming faith into beakers. The amount of science provided equals 10 x the number of followers of other religions in the target city. Accordingly, Missionaries, who may have little impact on the religious composition of the target city, can be a very cost-effective way to maximize the benefits of this belief. Note that you will need open borders treaties with your targets (to avoid losing Missionaries through attrition) and that you cannot earn science from Interfaith Dialogue by spreading your religion to cities that have only a pantheon or have no majority religion.

What enhancer beliefs will best help me spread my religion?

Of the nine enhancer beliefs, six will directly assist you in spreading your religion. Of those six, three beliefs enhance passive religious pressure, while the other three enhance manual spread:

• The Itinerant Preachers enhancer belief extends the effect of each city's pressure to 13 tiles, from the default 10 tiles. This 30% increase in pressure radius results in city pressure covering 69% more of the map, dramatically increasing the number of cities in range of each city's pressure.
  
  
• The Religious Texts enhancer belief increases the religious pressure each city exerts on cities within 10 tiles by 34% (and 68% after researching Printing Press). Although the range of Religious Texts remains 10 tiles, each city's religious pressure will exert 8 pressure (and later 10 pressure, after Printing Press is researched) on cities within a 10-tile range.
  
  
• Religious Unity spreads your religion to friendly city states at double the normal rate. Although the increase in pressure is useful, the requirement that you be friends with the targeted city state makes this belief somewhat less useful than Itinerant Preachers and Religious Texts, but it can still be useful in speeding the spread of your religion.
  
  
• Holy Order reduces the faith cost of Missionaries and Inquisitors by 25%. This allows you to purchase more Missionaries more quickly, allowing you to manually convert more cities more quickly.
  
  
• Messiah reduces the faith cost of Great Prophets and increases their conversion strength by 25%. As with Holy Order, this belief allows you to generate more powerful Great Prophets more quickly, allowing you to manually convert more cities more quickly. The reduced cost of Great Prophets also allows you to generate Great Prophets to create Holy Site tile improvements, which can be very useful in culture games.
  
  
• Missionary Zeal increases Missionary conversion strength by 25%. This belief has marginal utility, primarily allowing you to convert larger cities (those with population above 10) on a single spread.

The remaining three enhancer beliefs provide certain benefits from spreading your religion, but do not make passive or manual spread more effective:

• Defender of the Faith provides a 20% combat bonus near friendly cities that follow your religion. This bonus is similar to the Ethiopian Unique Ability combat bonus when fighting civilizations with more cities.
  
  
• Just War provides a 20% combat bonus near enemy Cities that follow this Religion. This bonus is similar to the Celtic Pictish Warrior's combat bonus when fighting outside Celtic culture borders.
  
  
• Reliquary provides 50 each time a Great Person, including a Great Prophet, is expended. For Great Prophets, the benefit is earned either at the time a Holy Site tile improvement is created or after the Great Prophet's last conversion spread. The amount of faith provided is underwhelming, but does apply to all Great Persons, which may be useful if you anticipate using specialists to generate a large number of Great Persons.

How do I defend my religion?

Just as there are two ways for you to spread your religion, other civilizations can use the same methods -- manual conversions with missionaries and Great Prophets and passive pressure -- to convert your cities to their religion. Combating manual conversion is fairly straightforward, with five tools available to you:

• Passive unit blocking -- Like other civilian units, Great Prophets and Missionaries can be blocked by military and civilian units. Since Great Prophets and Missionaries must be next to the city center in order to convert the city, you can use extra units (workers, other Great Persons, and military units) to deny them access to the city center. With enough units (and effort), you can also pro-actively "herd" Great Prophets and Missionaries out of your culture borders and, if you are lucky, into the path of some barbarians or a civilization with which they are at war.
  
  
• Deny Open Borders -- As noted above, Missionaries that spend too much time inside the culture borders of a civilization without an Open Borders treaty will suffer attrition. Denying Open Borders to a civilization that is sending numerous Missionaries into your culture borders will not necessarily deter them from continuing to do so, but those Missionaries will begin to experience attrition, reducing their effectiveness. But, it is important to keep in mind that Great Prophets do not experience attrition and can travel anywhere.
  
  
• Use Inquisitors -- As described in greater detail below, Inquisitors can play a helpful role in combating the spread of other religions.
  
  
• Demand That Conversions Cease -- After one or more of your cities has been converted to another religion, you will have a diplomatic option to demand that the other civilization cease sending Great Prophets and Missionaries into your lands. Like other diplomatic demands (such as the "stop spying" demand), you may be ignored by the other civilizations.
  
  
• Declare War -- As with any other unit, capturing or killing a Great Prophet or Missionary is an act of war. Depending on the circumstances, a Declaration of War may make sense as a method of dealing with Great Prophets and Missionaries, in addition to accomplishing other military goals.
  
  Note that captured Great Prophets and Missionaries retain their original religion. If you were to use them to spread your enemy's religion to other civilizations, you will be accused of proselytizing, not the founder of that religion. Great Prophets (and to a less effective extent, Missionaries, since they are subject to attrition) can be used as scouts or to provide visibility for siege units; Great Prophets can cross all culture borders without open borders treaties, but do cost maintenance, have only 2 movement points, are subject to all terrain movement penalties, and cannot pass through units of other civilizations. A captured Great Prophet that has 4 or more conversion spread uses left can also be used to found or enhance a religion or create a Holy Site tile improvement, but a captured Great Prophet with 3 or fewer conversion spreads left can only be used to spread his religion or serve as a mediocre scout.

How do Inquisitors work?

Inquisitors serve several important purposes to combat the spread of other religions to your cities:

• Deterrence -- An Inquisitor will deter other civilizations’ Great Prophets and Missionaries from manually spreading their religion to a city in which the Inquisitor is located. If an Inquisitor is located inside a city's culture borders, foreign Great Prophets and Missionaries will avoid that city and direct their attention elsewhere. It is not always necessary that you invest in a separate Inquisitor for each of your cities. So long as you have a decent road network, it should be sufficient to invest in one or two inquisitors to shuttle among your cities in response to threats. Sometimes civilizations may send multiple Great Prophets and Missionaries at a time, forcing you to rely on both Inquisitors and passive unit blocking to combat the threat. Note, however, that Inquisitors do nothing to combat passive spread from religious pressure. If you are experiencing massive religious pressure from your neighbors, you need to actively convert their cities to balance the pressure.
  
  
• Purge Heresy -- An Inquisitor can purge all other religions from a city that you own (this is the only Inquisitor effect that can be replicated by a Great Prophet). Note that this can only be done in cities that you own (including puppeted and annexed cities) and it will consume the Inquisitor, so you should think carefully about whether that is the best use of a valuable Inquisitor. Also take care not to purchase your Inquisitor in a city of another religion; Inquisitors take their religion from the city in which they are purchased, and if you try to use an Inquisitor of another religion to restore your religion in a city, you will instead extinguish your religion in that city.
  
  If the converted city (including your holy city) is located deep within your religion's borders, and subject to high pressure from surrounding cities that still have your religion, the city will likely reconvert to your religion in a reasonable number of turns and, in the meantime, that city will enjoy the benefits of its new religion, which may allow you to, for example, buy a new religious building in that city, capitalize on a temporary production boost, or take advantage of some other helpful pantheon or follower belief.
  
  
• Extinguish Holy City Status -- An Inquisitor can extinguish the Holy City status of an enemy Holy City that you have conquered (that use also consumes the Inquisitor). The city may still eventually reconvert to its former religion, if there are enough other nearby cities with its same religion, but it will not recover its Holy City status and will no longer experience the unique internal holy city pressure.

If you do choose to invest in some Inquisitors, you should try to do so before you leave the Medieval or Renaissance Eras, when Inquisitors are less expensive. At Standard speed, Inquisitors (like Missionaries) will cost 200 in the Medieval Era and 300 in the Renaissance Era, with the cost escalating 100 in each subsequent era. You will have to pay maintenance on the Inquisitors, but that investment may be worthwhile, depending on the religious composition of your neighborhood.

How do I deal with pressure?

The best defense to passive pressure from other religions is to get your religion into as many cities as possible, as early as possible, all of which will exert reciprocal pressure on each other. Pressure from other religions can be an inexorable force, gradually converting cities at your religion's borders and potentially leading to a cascading collapse of your religion. If you are late in founding and spreading your religion, you may struggle with combating pressure from other, better-established religions. In those cases, you should heed the old adage that the best defense is a good offense. Dispatching several Great Prophets to convert the other religion's nearby cities may provide enough pressure relief to allow your religion to stabilize. Once the rapid expansion of your religion has ceased, and you have reached equilibrium with neighboring religions, passive pressure should not drive significant change in the religious neighborhood. As mentioned above, Inquisitors have no effect on passive religious pressure from other cities. Also, as noted above, the only religious building that has any effect on pressure is the Grand Temple. None of the other religious buildings -- shrines, temples, cathedrals, monasteries, mosques, pagodas or faith-providing World Wonders -- has any effect on pressure.

How can enhancer beliefs help me defend my religion?

Few of the enhancer beliefs will directly assist you in defending against the spread of foreign religions. By effectively increasing your own religion's inter-city pressure, Itinerant Preachers and Religious Texts do have defensive benefits. By reducing the cost of Missionaries and Inquisitors, Holy Order can be helpful defensively. By reducing the cost of Great Prophets, Messiah also has modest defensive benefits. However, since the cost of Great Prophets quickly escalates, the benefits are fleeting, at best.

Conclusion

If you choose to invest in a religion, you should think about how best to spread your religion to other cities and to defend it from other religions. You have many tools available, from carefully selected founder and enhancer beliefs to pressure mechanics and strategic use of Great Prophets, Missionaries and Inquisitors, to achieve your desired victory condition.