Can Shias fight?

The Derb asks in an email:

Here's a thing I have been wondering about, in the context of a possible Iraqi civil war: Are Shias any good as fighters?

I ask because I am not clear how the Sunni minority managed to maintain its grip over the Shia majority in Iraq for all those decades. **And** I have been wondering for some time why the Iran-Iraq War was such a stalemate, when Iran's population is nearly 3 times Iraq's (70m vs. 26m).

Modern Arabs are supposed to be hopeless at war. (Moshe Dayan famously replied, when asked the key to success in modern warfare: "Fight Arabs.") Could it be that the Shias, both Arab and Persian, are even less warlike than Sunni Arabs?

Any thoughts?

The Spectator notes:

Strictly speaking, the last war of aggression launched by an Iranian monarch was in 1739, and since that time, the Iranian state has largely been on the defensive.