A remarkable feature of Canada’s external relations in the years between the two world wars of the twentieth century is the extent to which Canada’s conduct and speeches by its representatives on international affairs were dominated by imagery of North American harmony. Past clashes, most notably the War of 1812, or simply differences of views were forgotten or overlooked in the construction of a myth that served to justify inaction and the denial of commitments in imperial and world affairs. An aloof, unhelpful stance internationally was depicted more positively as a worthy example of peaceful attitudes and conduct. Thus, the inter-war period was dominated by rhetoric about ‘the longest undefended border in the world,’ ‘[more than a] century of peace in North America,’ and the contrast between the ‘New World’ and the ‘Old World’ in world affairs. No Canadian speech in an international forum seemed complete without some variation on these themes and without an admonition to Europeans and other miscreants to settle disputes by conciliation, negotiation and arbitration – rather than resort to war – as was the tradition in relations between Canada and the United States. This paper deals with the development, application and effect in the inter-war period of the lessons supposedly drawn from the experience and especially the aftermath of the War of 1812.