some hours after H-hour. One of these was destroyed after its parachutes failed to deploy, while another was damaged. As of 2009, this marked the first and only combat air-drop of tanks in history. The Sheridan was praised for its performance in Panama. A U.S. after-action report noted that the Sheridan's "extreme psychological effect on enemy forces" who were apparently deterred from firing at U.S. forces reinforced by tanks. In the early days of Desert Shield, Sheridans were airlanded in Saudi Arabia before coalition heavy armor arrived by ship. The first Sheridans sent were the M551A1 model. The Army hastily sent 60 M551A1 TTS models with the thermal sight upgrade to replace the older models. The 3/73rd used the Sheridan as part of a flanking force in Operation Desert Storm, and saw tank-on-tank combat. Their role was limited to reconnaissance due to their age and light armor. It is likely that no more than six Shillelagh missiles were fired at Iraqi anti-tank guns or T-55s; this was the only occasion in which Shillelagh missiles were fired in anger, from the inventory of 88,000 missiles produced. Other than some overheating problems in the summer months of the buildup, the Sheridan suffered no mechanical breakdowns in combat and performed extremely well. Australian trials During 1967 and 1968 the Australian Army trialled two Sheridans to determine if the type met a requirement for light armored fighting vehicles to serve with the Royal Australian Armoured Corps newly formed cavalry regiments. The main trials took place in the tropical Innisfail area of north Queensland between January and June 1968. In January 1969 the Minister for the Army announced that Australia would not purchase any Sheridans as the tanks did not meet the Army's requirements. The main shortcoming revealed in the trials concerned the safety of the combustible case. The two Sheridans were returned to the U.S. Army in early 1969, and the Australian Army met its requirement by fitting turrets from Alvis Saladin armoured cars to M113 armored personnel carriers. Replacement In 1977, TRADOC commander General Donn A. Starry met with Army Chief of Staff General Edward C. Meyer to convince him that the service should retire the Sheridan. Starry had commanded the 11th ACR in Vietnam, and knew the vehicle's shortcomings. Starry's arguments prevailed over those of Army Material Command commander General John R. Guthrie, a Sheridan defender, and Meyer agreed the Sheridan would