On 4 April 1949, in the auditorium of the State Department on Washington’s Constitution Avenue, the foreign ministers of Canada, the United States, the United Kingdom, France and eight other countries signed the North Atlantic Treaty. An armed attack on one member, the treaty’s Article 5 pledged, would be an armed attack on them all.
The leading historian of the event called it a Second American Revolution, radically transforming United States foreign policy. It was no less a revolution for Canada. North America was engaging itself in the security of Europe for the long haul.