Operation Double Eagle, carried out by U.S. and South Vietnamese marines, was a complementary mission to Operation Masher in neighboring Quảng Ngãi Province adjoining Binh Dinh province to the north. Operation Double Eagle was carried out over an area of about about north to south and extending as much as inland from the South China Sea. 6,000 regular troops and 600 guerrillas were believed to be operating within this area. U.S. Marines dedicated to the operation would number more than 5,000 plus several thousand South Vietnamese soldiers of the ARVN 2nd Division.