Claire Short, like Robin Cook, will almost certainly go now, they had both said they would if war went ahead without a 2nd UN resolution.
But Short was for the action in Kosovo in 1999, however she would not have been pleased by being called 'Bomber Short' ever since by the left, who regarded her as one of their own.
If you think that he quit for his principles you are mistaken. He's quit to further his own political ambitions. With Blair on a sticky wicket Cook thinks he will be ideally placed to replace him. Notice how he was desperate to be first to go especially when Short had already announced that she would resign.
And another thing, how can you trust someone as weird looking as him?