FOUR prisoners described as dangerous enemy combatants escaped from the main American military base in Afghanistan yesterday, the latest embarrassment for commanders there who were already struggling with their worst military losses in four years.A huge manhunt, using helicopters and American ground forces, was under way after the four men were discovered missing from the heavily fortified prison at the Bagram air base, north of Kabul. American military officials would not comment on the identities of the men but an Afghan official said that they were all from Arab countries and suspected al-Qaeda members. Kabir Ahmed, the district chief of...