Similar thing like Endoperez' Knights happened to me.... laying siege to Man's home citadel, I was informed that a barbarian horde attacked and tried to pillage the province. Hum. Twice, actually... two Messages of the same kind in the same turn, both for the same province, right after the other.
Nothing happened, though. Next turn, I stormed the castle, and frankly forgot about the barbarians who never came.
The turn after that, I got the information that the enemy has captured my undefended province... and lo and behold, the barbarian horde was outside my castle walls.
