In October 1962, the Cuban missile crisis became a 13-day confrontation between the Soviet Union and Cuba on one side and the United States on the other, and is generally regarded as the moment when the Cold War came closest to nuclear conflict. The United States considered attacking Cuba by air and sea but instead imposed a military blockade, called a quarantine, while demanding that the Soviets stop delivering offensive weapons to Cuba, dismantle missile bases under construction or already completed, and return all offensive weapons to the USSR. Although the Kennedy administration expected a military confrontation and Khrushchev denounced the blockade as an act of aggression, secret back-channel communications opened a path to settlement even as several Soviet ships tried to run the blockade and U.S. Navy ships received orders to fire warning shots and then open fire. Tensions rose further on October 27, when a U-2 was shot down by a Soviet missile crew, but Kennedy did not retaliate and negotiations continued. The confrontation ended on October 28, 1962, when Kennedy and United Nations Secretary-General U Thant reached an agreement with Khrushchev under which the Soviets would publicly dismantle their offensive weapons in Cuba and return them to the Soviet Union under United Nations verification, in exchange for a U.S. public pledge not to invade Cuba, while the United States secretly agreed to remove Jupiter IRBMs from Turkey and Italy. After the missiles and Ilyushin Il-28 light bombers were removed, the blockade formally ended on November 20, 1962, and the crisis also led to the creation of the Moscow-Washington hotline. Cuba viewed the outcome as a partial betrayal because Kennedy and Khrushchev made the decisions on resolving the crisis without Cuba, and Castro especially resented that issues such as the status of the U.S. Naval Base in Guantánamo were not addressed, contributing to years of deteriorated Cuban-Soviet relations even as Cuba remained protected from invasion.