DOVER AIR FORCE BASE, Del (Reuters) - President Barack Obama flew to a Delaware air force base on Tuesday to honor the return of the remains of 30 U.S. troops killed when Taliban insurgents shot down their helicopter in Afghanistan. Obama, after vowing he would be undeterred in his war strategy, led a delegation of U.S. officials paying tribute to those who lost their lives in the single deadliest incident for U.S. forces in Afghanistan. The visit appeared intended to show war-weary Americans that the president recognizes the human cost in Afghanistan. He unveiled a troop drawdown plan in June to start winding down U.S. involvement in the unpopular, nearly decade-old conflict.