Terrain
Terrain plays a key role in all wars. This can be a pretty big topic so it might take awhile to get through this. First, I want to go through the different terrain you can encounter and discuss briefly their importance regarding both logistics and the resources they may possess. Next, I hope to get some screenshots of random maps and discuss some things to think about when settling cities and invading your neighbors. Why settling cities? Proper city location can prepare you for future wars while poor settles can make your life harder. While this thread is about offensive wars, there will be situations where you need to go from defensive to the offensive so avoiding defensive wars doesn't make sense.
Unimproved Terrain
Coast:
2

Food, 1

Movement Expended
Until you unlocked Compass, you will be stuck traversing on the Coast (unless you're Polynesia) for early game and part of mid game. Therefore, your naval combat will take place entirely on coastal tiles. Once you unlock Fishing, then your land units can embark and that can greatly change how wars take place. Coastal cities can be vulnerable or impenetrable depending how many coastal tiles are adjacent to the cities.
The only strategic resource found on a Coast tile is Oil. For the late game, oil can be very important as it's needed for air and armored units. For games that do last that long to end, you don't want to lack Oil.
Desert:
2

Movements Expended
Deserts are one of the biggest natural barriers available to you. They are often much better for the defender than the attacker. When planning wars, it's vital to plan for Deserts because they can slow your advances to a halt at times. Desert tiles limit your non-mounted units to only 1

Movement and mounted units lose 2

Movements. These can be detrimental if a speedy war is something you're aiming for. At least Desert tiles don't obstruct direct fire for ranged units.
Desert tiles can potentially spawn four strategic resources: Iron, Oil, Aluminum and Uranium. Iron is very important early game while the other three resources are really geared for late game.
Grassland:
2

Food, 1

Movement Expended
There's not much to be said about Grassland other than that they don't obstruct your advances. For mounted units, an open terrain of just Grassland can really give them a chance to shine, especially those Chariot Archers.
Grassland tiles can potentially spawn four strategic resources: Iron, Horses, Coal and Uranium. Iron and Horses and very important early game while Coal is vital mid game.
Hill:
2

Production, 2

Movements Expended. +10%

Bonus
Like Desert tiles, Hill tiles also uses up 2

Movements. Unlike Desert tiles, Hill tiles also greatly complicates combat with how vision, direct fire works and defensive bonus. Defensive bonus is the most straightforward as units stationed on a Hill tile is harder to kill (note the bonus doesn't apply when you're attacking).
Regarding vision, units usually have a default vision of 2 tiles (correct me if I'm wrong). If the unit is on flat terrain like Grassland or Desert and is adjacent to a Hill tile, then that unit, despite have 2 tile vision, can't see the tile blocked by the Hill. Intelligence on the enemy is very powerful so lack of vision can actually make wars ineffective. Knowing where you enemy units are at is half the battle as you'll make better decisions from what you know. However, it does differ where you can see a hill 3 tiles away as opposed to only 2 tiles away. See screenshot below for clarification about vision with Hill tiles:
The third aspect, direct fire, matters throughout the game but it's more apparent early game where indirect fire promotion is nonexistent. Hills can prevent ranged units from supporting melee units and, when ranged units provide a lot of the damage early game, that can make pushes extremely difficult. Luckily for humans, AIs don't take into account of this factor so it's likely they settle cities that cannot target ranged units while nearby hills can provide the attackers an edge. If a ranged unit is on a hill, it can fire over any adjacent tiles except for Forest/Jungle Hill tiles.
Hill tiles can potentially spawn four strategic resources: Iron, Coal, Aluminum and Uranium
Forest/Jungle Hill:
2

Food, 1

Production, 3

Movements Expended. +35%

Bonus (Jungle, Plains/Forest, Grassland)
1

Food, 2

Production, 3

Movements Expended. +35%

Bonus (Forest, Plains)
Forest/Jungle Hill tiles expend 3

Movements as opposed to the normal two. Take that into account when moving mounted units, especially the ranged ones, because it can leave them very exposed. Forest/Jungle Hill tiles also blocks all direct fire from all ranged units and vision for all units in adjacent tiles except maybe Mountains (hope someone can confirm or deny this). These hill tiles also give more

Bonus so use that to your advantage when moving your melee units forward. See screenshot below for clarification about vision with Forest/Jungle Hill tiles:
Forest/Jungle Hill tiles can potentially spawn the same strategic resources as Hill tiles. (Need confirmation for whether they might also spawn Oil for Jungle Hill Tiles.)
Desert Hill:
2
Production, 3
Movements Expended. +10%
Bonus
Desert Hill tiles also slows down movement drastically but it at least doesn't cause more issues to ranged units like Forest/Jungle Hill tiles. These hill tiles also provide the same amount of

Bonus as ordinary hills.
Desert Hill tiles can potentially spawn the same strategic resources as Hill tiles.
Mountain:
Impassable except certain conditions, +35%
Bonus (someone confirm if

is 10/25/35%?)
The Incans can traverse Mountain thanks to their UA. There are other promotions like Hovering Unit (for Zeppelin and Helicopter Gunship) and Engineering Corps (though I don't know what units gets access to this). If a Worker builds a road on Mountains, then all units can traverse it like a hill.
Ocean:
1
Food,1

Movements Expended
Ocean is a very interesting when it comes to its importance. Early game, you won't be able to traverse unless you're Polynesia. Depending on what map you play on, naval combat can play an important and you'll see a fairly big portion of the battles happening both on Coast and Ocean tiles. In addition, you get larger discount on your tech if you meet more AIs that are ahead of you can those extra shaved turns can matter for the timing of your military techs. When there are large stretches of Ocean tiles, extra

Movement and vision can play a greater role in dealing a devastating blow to your enemy's forces or withdraw with most of your units to fight another day.
Ocean tiles can potentially spawn Oil.
Plains:
1
Food, 1

Production, 1

Movements Expended
Plain tiles are bland like Grassland and there isn't much to be about them except that they can spawn the most strategic resources out of all the tiles mentioned so far and these can help both early, mid and late game.
Plains tiles can potentially spawn five strategic resources: Iron, Horses, Coal, Aluminum and Uranium.
Snow:
2

Movements Expended
In most cases, Snow tiles won't play any role in your wars. AIs will settle bad cities that requires you to go through Snow tiles but those cities won't be relevant if you capture the other (and often core) cities already or if you have vassalage enabled.
Snow tiles can potentially spawn three strategic resources: Iron, Oil and Uranium.
Tundra:
1
Food,1

Movements Expended
Tundra tiles aren't great but they at least give some nice strategic resources if RNG goes your way.
Tundra tiles can potentially spawn five strategic resources: Iron, Horses, Oil, Alunimum and Uranium.
Features
Atoll:
2
Food, 2
Production, 1
Movements Expended
Atoll gives decent yields but otherwise is no different a Coast tile.
Atoll tiles don't spawn any strategic resources.
Fallout:
-3
Food, -3
Production, -3

Gold, 2
Movements Expended. +5%
Bonus
Fallout is caused when anyone used a nuke. It slows down advances, provides a tiny bit of

bonus and deals 15 damage to any units ending their turn in it. In my opinion, fallout will slow down your conquest a lot due to the heals required and the extra

Movement expended unless you have enemy in a really fortified position and grinding through it will take longer. In the scenario where you opponent gambled everything at defensive position, a nuke can devastate that defensive position and make rest of the war easier due to how much weaker other cities will be defensively. You can unlock the promotion, Fallout Resistance and Fallout Immunity, from very late techs to minimize or avoid taking damage from Fallout but that's one less promotion for that unit. (I need confirmation but do Workers eventually get the ability to clean Fallout tiles? I can't seem to find where on the tech tree that gives them the ability)
Forest:
1
Food, 2
Production, 2
Movements Expended. +25%
Bonus (Forest, Plains)
2

Food, 1

Production, 2

Movements Expended. +25%

Bonus (Forest, Grasslands)
Forest can be quite interesting in that they really hinder melee units (by limiting movement to only 1) and ranged units (by limiting the range to 1 unless the unit has Indirect Fire promotion) while helping mounted units that excel on hit and run tactics. For instance, ranged mounted units like Skirmishers can do quite well where they move into a Forest tile, attack a unit and back away with impunity except for some special cases. In addition to the movement limitations, Forest tiles also affect vision.
Forest tiles causes same vision obstruction like Hills. See the screenshots below for clarification about vision with Forest tiles.
Forest tiles can potentially spawn Uranium and Iron.
Flood Plains:
3
Food, 1
Movements Expended. +5%
Bonus (need confirmation about the

bonus)
Flood Plains tiles are really bland as they act as ordinary tiles. If there is indeed

bonus, then they are slightly better than other flat tiles. This tile is mostly good for city growth.
Flood Plains tiles don't spawn any strategic resources.
Ice:
Impassable except for special cases
Ice tiles, like Mountain tiles, can be traversed with certain promotions. Engineering Corps and Hovering Units Promotion (both of which applies to Mountain as well) along with May Enter Ice Tiles promotion (for Submarines) allow units to pass over Ice
Jungle:
2
Food,
1
Production, 2
Movements Expended. +25%
Bonus (Jungle, Plains)
Jungle tiles function much like Forest tiles.
Jungle tiles can potentially spawn Oil and Uranium.
Marsh:
3
Food, 3
Movements Expended. +5%
Bonus
Marsh tiles are basically Desert tiles that force you to expend one more

Movement. Considering that this terrain is considered flat, it's awful if it's surrounded by Forests and Hills for practically all units. As a result, Marsh tiles literally bogs down your forces but, for defending purposes, it's actually amazing. No UA or UU (at least that I know of) can make good use of this terrain so the attackers are slowed down drastically both advancing and withdrawing. I have noticed the Marsh Walkers promotion that apply to Barbarians on Civilopedia but I don't know if this promotion still gets used. Otherwise, that double movement can be quite strong for certain maps.
Marsh tiles can potentially spawn Uranium and Oil.
Oasis:
3

Food, 2

Gold, 1

Movements Expended. +5%

Bonus
Oasis tiles may appear like a vastly improved Desert tile but it can actually play a big role in battles. As mentioned earlier, Desert tiles are one of the natural barriers you can face. Since Oasis only expends 1

Movement as opposed to 2, it can potentially give you some interesting maneuverability. Now, this is a niche situation but the extra movement can play a bigger role than you can imagine and therefore place you cities with the location of Oasis tiles in mind.
Rivers:
Lose all movements crossing it except for special cases
Rivers aren't tiles since they exist between tiles. Their existence can cause wars to be won or lost depending on where battles take place. In the early game, Rivers will make all units lose their movements regardless if there are roads or not (Engineering will enable bridges over roads that cross Rivers). The only exception to the rule is Songhai which excels with Rivers. For all the other civs, Rivers can be the best defense against invasions or the biggest obstacle for any offensives. More details about how valuable Rivers are will be discussed later as we get to screenshots and my discussion of city settling and invasions.