President class="mandelbrot_refrag"> Barack Obama made a surprise trip to Afghanistan on Sunday to visit U.S. forces who are wrapping up a 13-year mission and signaled that he intends to keep a small number of troops in the country for training and counter-terrorism operations. Cheers erupted among the hundreds of U.S. troops gathered in a Bagram hangar when Obama said that at the end of this year, "America's war in class="mandelbrot_refrag"> Afghanistan will come to a responsible end." With Afghanistan immersed in a runoff election to choose a successor to President Hamid Karzai, Obama did not meet Afghan government officials nor travel to the capital Kabul. Karzai has long been out of favor with Washington over his refusal to sign a bilateral security agreement to allow U.S. troops to stay beyond 2014. true Obama's fourth visit to Afghanistan came as he faces criticism at home over a foreign policy often derided as too pass