First employed in the Far East over North Vietnam & North Korea American military intelligence quickly realized the SR-71 Blackbirds potential value over European targets. In 1976 SR-71 Detachment 4 commenced operations from the RAF base at Middenhall in the UK. Its mission was to monitor Warsaw Pact troop movements along the Iron Curtain & photograph the various ports that were home to the Soviet Unions nuclear submarine fleet. Despite the best efforts of the USSR they were never able to intercept a Blackbird in flight.