BIN JAWWAD, Libya (AP) — Rebel forces on Monday fought their way to the doorstep of Moammar Gadhafi's hometown of Sirte, a key government stronghold guarding the road to the capital Tripoli, their rapid advance built on powerful international airstrikes that have battered Gadhafi's air force, armor and troops. The rebels' offensive has restored to the opposition all the territory they lost over the past week and brought them closer than ever to Sirte, with their fighters advancing to within 60 miles (100 kilometers) of the bastion of Gadhafi's power in the center of the country. But the advance on Sirte and the flip-flop in the conflict's momentum brought into sharper relief the central ambiguity of the international mission in Libya.