BAGHDAD - Warning sirens wail and within seconds rockets and mortars strike — sometimes one or two, other times 10 or more. The Green Zone is again a prime target as American and British diplomats, Iraqi politicians, contractors and others struggle to go about their business — always aware that any time they are outside the most fortified buildings there is a chance to be injured or killed. The danger has temporarily reshaped life: Green Zone traffic is minimal, few people venture out on the streets and security precautions — always high — have been boosted. Many diplomats and others...