You cant complete caucasus from 1 warlord in 2 turns
That is not entirely true. If both 4vs2 attacks lose one army, you can make three 3vs2 attacks next turn.
0,6 * 0,6 * 0,8 * 0,8 * 0,8 = 18,432%
It's slightly more, because if you lose more troops first turn, you use some 2vs2.
But overall it's below 20%.
Edited 7/13/2014 16:48:09