Whoever is coding AI troop movement needs to get their head out of their as...water.

The frequency that the AI will throw units into the water is just ridiculous. I play on immortal.

scenario 1:
A distant CS ally is surround by water with 2 single tile passes thru the mountains. I check to see if I should send any assistance to hold, but they look in great shape with a melee unit in both passes backed by 4 ranged units that can hit any enemy attacking either pass. A few turns later, the nearby Ai declares war on them with a massive fleet (whoops, didn't see that coming from a size 3 city). The small CS fleet is sunk (kudos to improved AI naval combat), but the passes hold as expected. So now its the CS turn to move, and every unit jumps into the water. WTF!!!! Of course the AI fleet sinks every unit that it can reach and floods thru the now unarmed passes. And the CS relands their units where they both die the next turn.

The ranged units and city could easily have sunk a few AI ships each turn, so even tho there were over a dozen AI coast hugging ships, the odds of the CS falling were slim had the land units just held their ground, because those passes were not going to be taken by the AI land units on hand.

Scenario 2:
AI ally builds a city on a 2 tile island, and puts a ranged unit on both tiles. War breaks out and a small enemy fleet with a few melee units shows up. Sure enough, both allied units immediately hop in the water leaving the city to fend for it self.

Scenario 3:
Enemy city is nestled between some hills and lakes. My ranged units are having a hard time staying close to hit the city because enemy melee units hit them as soon as they get close to the city. So I send some expendable melee units on an end around hoping to draw the enemy melee units away from my ranged units. But no need for such an elaborate plan because after a few turns, all of the enemy units jump into the lakes within range of my ranged units where I am happy to sink them. The assault on the city took forever as I came in understrength compared to the city strength. So the enemy had time to generate a few units, and each of those units immediately moved into the lake next to the city and were promptly sunk.

Every time I watch a coastal battle, it is the same thing with units jumping into the water for no reason. This really needs to be fixed. I know that in general, AI units are not very smart, but this is just moronic. I suspect part of the problem is that AI units are coded never to just pick a tile and camp out there. It is just hilariou to watch 2 of the same units swap tiles every turn. I know that this isn't a war game, but war is a big part of the game, and deserves a better ai.

Had a recent game a whole bunch of seige towers cane attacking and once a few where taken out the ai embarked a bunch and proceeded to lose a bunch more because of this stupid programming

Charlie don't surf but the AI sure does... This is high on the [censorship sucks] scale, right up there with Great Works running out. How it's survived this far I'll never fathom (it was in vanilla and G&K, too). Just make a simple rule: never embark if enemies can shoot you. You could still camp out of range and move your ships in once they're in the water but hey, it's a band-aid on a gushing wound and anything helps.

Sadly, I suspect it's the AI trying to be clever. It retreats its army behind the fog of war if it knows it can't take you. It also retreats to the water if it thinks it'll lose on land. Ultimately it underestimates its strength, particularly it's ranged strength, and as has been noted, doesn't check for ranged or naval threats prior to embarking.

Personally, I think the solution needs to be multi-pronged. It needs to better assess its ranged strength. It needs to retreat behind a city and try and hold, rather than run and sacrifice the city. It should understand that most wars will be one-city affairs. Either it will save the city by destroying the invading army and win, or it'll lose the city and immediately negotiate peace. Better to fight for that city than jump into the water like lemmings.

AI during wars is the Achilles' heel of the whole game. Unless AI learns how to create and uphold a front line, its efforts will always be pathetic. At this point of the game's development, AI is unable to hold important pieces of ground and only rushes towards enemy or retreats in unruly fashion. AI needs to be able to identify points of strategic interest, like bridges on neutral terrain or forested hills. Inability to do so is the cause forcing AI to scatter their troops for no apparent reason.

We've got a very similar situation when it comes to combat in air. In most cases, I'm able to destroy all enemy air force in 2-3 turns. AI simply sends their bombers and fighters against one target and if there is enough anti-air land troops and fighters, it's just slaughter. Has anyone ever seen AI performing an air-sweep mission or avoiding areas covered by fighters? It's just one more case of mindless rushing.

Yes they are coded for air sweep but how well I don't know.

Makavcio I think I have a lead on the problem you talk about.

The AI is trying to hide it's army in the fog of war. If it manages to do that it can organize quite an effective army. However if it is in the visibility of the enemy, it's organisation collapses as it tries to find fog of war tiles.

Only a hunch.

It is a big weakness in Civ5. A decent army cannot hide in the FOW because the tile resolution is too low for 1UPT. This single issue means that you sometimes have armies that are taking up large areas of the map but are sitting ducks because humans can see them.