An army of 1400 Cuban exiles opposed to Castro, recruited, trained and financed in secret by the United States, invaded their country in the Bay of Pigs. US President John F. Kennedy, annoyed by the two years of Communist regime in Cuba, approved the invasion but, at the last moment, refused to order air support when the operation appeared to be doomed to failure. Within a period of three days, the invasion forces, abandoned by Kennedy and the American military, were forced to surrender to the Communists. About 100 Cuban exiles were killed in the fight. The disastrous operation was a huge humiliation for the Kennedy administration and significantly increased the tensions of the Cold War. Castro refused to return the surviving Cuban exiles until the United States sent millions of dollars in humanitarian aid to Cuba.