like it, especially the road + fortress team. I must try that
I think I shared this somewhere else, but I will again... ha ha!
Frequently I play with 31 civs with no victory conditions, and just tend to be a global peacekeeper trying to keep all the civs alive. So in 1 epic game I was playing I discovered that the Russians (I think, was a long time ago) were about to be wiped out. They were across the ocean from me, and I had no cities or troops over there to help them.
I ended up sending over Riflemen and workers, and had to fight through several other civilizations to get to the Russians. I used the road/fort technique and just stayed defensive. At one point my stack was completely surrounded by enemy troops, every square, large stacks, and held out. Eventually, using a chain of forts, I was able to get to and save the Russians. It remains one of my favorite campaigns. Fighting defensively is always more efficient, because 1 unit can take out many.
Currently my Roman army is fighting off the Greeks in northern Italy. They have 2/3 Hoplites against my 1/2 Spear and 2/1 Archers. I'm just fortifying cities and letting them wreak havoc around my two border cities until they attempt to cross a river or move over a hill, and then I race some troops out (provided there are roads so I can move and fortify in the same turn) and defend. In the meantime, I'm increasing the tech gap by building lorehouses (+ tubes) and harbors (+gold) and laughing at stupid Alexander. Soon I will pay the Scythians to declare on him, and watch his ambition and greed lead to his ruin.
In another favorite campaign, in a story I had started, it was the Russians, conversely, who were my enemy. They started with something like 30 cities (on a map with zero corruption), and I had 1. During a critical expansion stage, when the Russians were far ahead in techs, I kept building border cities between the Russians and myself, defending them as long as I could, and then I would raze them before the Russians would take them, and retreat to save my troops. During peace, I would rebuild the cities I had razed, thus preserving the heart of my little kingdom from Russian incursion while I conquered lesser enemies and colonized coastal/island cities (key to winning on that map).
Crusaders are another great unit for defensive campaigns - 5/3 and can build forts.