PORT HARCOURT, Nigeria - Militants battling for a bigger cut of Nigeria's oil revenue exploded a car bomb inside a military base, ending weeks of relative calm with a blast that killed at least two people and sent a fireball into the night sky. The Movement for Emancipation of the Niger Delta claimed responsibility for the blast late Wednesday at a barracks in the southern oil center of Port Harcourt. The group's attacks on oil installations in Nigeria, Africa's leading oil exporter, had already helped drive up world oil prices. This country is the fifth-biggest source of U.S. oil imports....