 While the Department of Defence advised the government that three to six submarines should be purchased for training purposes, following the intervention of then-Senator John Gorton the Government instead approved the purchase of eight submarines to form a submarine strike force.Eight British "Oberon" class submarines were ordered in 1964, to be built in Scotland in two batches of four boats.Only six boats were delivered; the seventh and eighth were cancelled in 1971 to fund the acquisition of ten A-4 Skyhawk aircraft for the Fleet Air Arm.