Four U.S. servicemen with the NATO-led force were killed by a roadside bomb in southern Afghanistan on Tuesday, the alliance said, making 2009 the deadliest year for foreign troops since the overthrow of the Taliban in 2001. The deaths bring the number of foreign forces killed in 2009 to 295, according to website icasualties.org, which compiles official data. The previous deadliest year was 2008 when 294 foreign troops died, Reuters reported.