from ap: A roadside bomb killed four U.S. soldiers in Baghdad on Sunday, the military said, pushing the overall American death toll in the five-year war to at least 4,000. The grim milestone came on the same day that rockets and mortars pounded the U.S.-protected Green Zone, underscoring the fragile security situation and the resilience of both Sunni and Shiite extremist groups despite an overall lull in violence.