For those who want to play crusades i want to tell you just this....assassins are like mega-uber overpowered ....you get from a fresh out of the slums assassin 95% chance to kill any merchant; diplomat; or priest ..... i took out the mongols(i have to be frank with this with about 20 assassins) in one turn

They should be repaired....but there is always the fun part of not letting your opponent convert your population to his religion...or those pesky thiefs and assassins.