In August 1949, earlier than U.S. intelligence analysts had anticipated, the Soviet Union tested its first atomic device. This event and the almost concurrent retreat of the Kuomintang regime from mainland China hastened debate within the administration as to whether the United States should develop a hydrogen bomb. Initially, Johnson suspected — despite confirming air samples — that the Soviets had not really tested an atomic device at all. He theorized that perhaps an accidental laboratory explosion had occurred, and that no reassessments of U.S. defense capabilities were needed.