Humvees and armor:

There was a piece in Slate today about the US army's lack of armored Jeeps in Iraq. One of the things that always surprises people in Belfast is that the army Jeeps there are entirely stripped down, no armor, not even doors or canvas roofs. Looking at them, you can usually see three or four soldiers (or RUC) crouching in the back. The argument is that the great visibility outweighs the greater danger that the soldiers are in, particularly when any sniper knows that there are actually about three other jeeps nearby.

I'm not sure why the same principle doesn't hold in Iraq. On the face at least, the two situations seem similar. A guerrilla war, fought with both bombs and bullets, against a determined but outgunned enemy in terrain that is both rural and urban (though I suspect that more of the war in the north of Ireland is fought in the cities than the war in Iraq is, since the British have more or less conceded the Irish countryside to the Catholics).