Brave New World, how to capture caravans?

[Vargas78]

I was at war with the Mongols and at one point an orange mongol owned caravan strayed out my city, there was a keshik nearby but most mongol forces were trying to take another city.

So i strayed out and managed to move to it's hex, but it didnt capture or plunder it, they just shared the square despite being at war. The caravan obviously then moved on the next turn and my Pikeman formerly guarding the city got peppered with arrows and hobbled back to town.

I remember in an earlier part of the game one of the american caravans coming to trade with me was attacked, it came up as a bulletin point as it had a small effect on my trade revenue (but not that big as i didnt actually own it) although i was not at war with the mongols myself at the time.

So how come mongols could attack the american caravan trading with me, when they were at war with the americans, and i couldnt attack the mongol caravan when i was at war with them?

[The Rock God]

After moving over the caravan you still have to plunder it.

[Vargas78]

Ah, pikeman was out of movement turns then.

[5n4k3d0cToR]

Gotta plunder mate and it expends 1 mov point.