WASHINGTON (AP) — President Barack Obama won’t walk away from the flagging war in Afghanistan, the White House declared Monday as Obama faced tough decisions — and intense administration debate — over choices that could help define his presidency in his first year as commander in chief.The Taliban attack that killed eight American soldiers over the weekend added to the pressure. The assault overwhelmed a remote U.S. outpost where American forces have been stretched thin in battling insurgents, underscoring an appeal from Obama’s top Afghanistan commander for as many as 40,000 additional forces — and reminding the nation of the costs of war.