On the ground in the eastern chunk of this oil-rich desert nation, the signs of rebellion are plain to see in the armories of a military base near Baida: Weapons crates lie busted open and empty. Rifles are missing from their racks. Left behind are helmets and gas masks and cleaning kits—things that can't shoot.

For four days, rebels newly armed with anti-aircraft guns and Kalashnikovs battled forces loyal to Libyan strongman Col. Moammar Gadhafi and commanded by one of his sons. After days of firefights, feints and an ambush...