The Cuban Missile Crisis began 22 October1962. Following intelligence reports that the USSR was installing ballistic missiles in Cuba capable of hitting US and Canadian targets, President John Kennedy announced an American naval blockade of the island, threatening further action if preparation of the sites continued. Informed of Kennedy's intentions only one-and-a-half hours in advance, the issue for the Canadian government was whether to comply with an American request to move Canadian forces to an alert status known as "Defcon 3." With the approval of Minister of National Defence Douglas Harkness, Canadian units quietly did so, but formal authorization was delayed while Cabinet debated October 23-24. Harkness argued that the nature of the crisis, combined with existing arrangements for defence co-operation, made the alert necessary.
Fearing a Canadian alert would provoke the USSR and believing the American Cuban policy to be generally unbalanced, angered by the lack of advance consultation and concerned about implications for Canadian policy on nuclear weapons, Prime Minister John DIEFENBAKER and Secretary of State for External Affairs Howard Green were reluctant to acquiesce to Kennedy. About half of Canada's ministers remained undecided, but as Soviet ships approached the quarantine zone later in the week the Harkness position gained support and on October 24 the Diefenbaker government authorized the Defcon 3 alert.
Canada's hesitant response reflected in part the desire of the prime minister and others to preserve the independence of Canadian foreign policy and to maintain a balanced posture in crisis conditions. The delay, however, was widely criticized and contributed to a growing perception of indecisiveness in the Diefenbaker government. It also exacerbated already difficult relations with the Kennedy administration and fuelled further controversy over nuclear weapons. The crisis itself ended October 27-28 when Soviet Premier Nikita Khrushchev agreed to dismantle and remove the USSR missiles in Cuba.