The current RC-135 fleet is the latest iteration of modifications to this pool of aircraft dating back to the early 1960s. Initially employed by Strategic Air Command for reconnaissance, the RC-135 fleet has participated in every armed conflict involving U.S. forces during its tenure. RC-135s supported operations in Vietnam War, the Mediterranean for Operation El Dorado Canyon, Grenada for Operation Urgent Fury, Panama for Operation Just Cause, the Balkans for Operations Deliberate Force and Allied Force, and Southwest Asia for Operations Desert Shield, Desert Storm, Enduring Freedom and Iraqi Freedom. RC-135s have maintained a constant presence in Southwest Asia since the early 1990s. They were stalwarts of Cold War operations, with missions flown around the periphery of the USSR and its client states in Europe and around the world.