Pinetree Line

1958 – History of RCAF Air Defence Command – National Archives of Canada

February 28, 1958


Prior to the end of the 1930’s, defence cooperation between Canada and the United States was practically non-existent. Colonel CP Stacey, Director of the Historical Section, General Staff, NDHQ, writing in the Spring of 1954 issue of the "International Journal" characterized Canada-United States defence cooperation in the period prior to the outbreak of the war in Europe in the following terms: "That it (defence cooperation) took place at all was due to a common sense of danger; that it was so limited was the result of the inhibiting conditions of the time and the desire of both countries to avoid commitments. … The approach to the problem on both sides of the border previous to the outbreak of war in Europe in 1939 was necessarily halting". Perhaps the stage was set for later defence cooperation between the two countries by statements made a few days apart in 1938 by the President of the United States and the Prime Minister of Canada. The President, speaking at Kingston, Ontario, said in part: "I give to you the assurance that the people of the United States will not stand idly by if domination of Canadian soil is threatened by another empire." A few days later the Prime Minister, speaking in Woodbridge, Ontario, said: "Should the occasion ever arise, enemy forces should not be able to pursue their way either by land, sea or air to the United States across Canadian territory."

In 1940 these commitments were institutionalized at the meeting of the Prime Minister and the President on August 18 at Ogdensburg, New York, when the Permanent Joint Board on Defence was constituted to "consider in the broad sense the defence of the northern half of the western hemisphere". From the very outset the Board was established as a permanent institution; it continues to function today as an advisory body, making recommendations on mutual defence problems through its respective national sections to the Canadian and United States Governments. During the course of the war it made some 33 formal recommendations to Governments covering a wide variety of defence activities and its influence was felt on countless other matters relating to the defence interests of Canada and the United States in war time.

On February 12, 1947, the Canadian and United States Governments issued a joint statement in which was set out the main principles which would underlie their continued collaboration in peace time in matters of defence interest. The principles which are summarized below were thrashed out in the Board and were announced to be in continuance of the pattern of close defence cooperation which had been established by the Board’s work during the war time period. The joint statement provided for:

[a] - the interchange of selected service personnel between the defence establishments of the two countries.

[b] - General cooperation in defence exercises and in the development and testing of material of common interest.

[c] - Encouragement of common designs and standards in arms, equipment, organization, methods of training and new developments; and

[d] - Mutual and reciprocal availability of military, naval and air facilities in each country.

The joint statement went on to say that "as an underlying principle all cooperative arrangements will be without impairment of the control of either country over all activities in its territory." This general statement of principles for defence cooperation between the two countries has been basic to decisions taken in the post war period to strengthen the continental defences.

In 1949 the Canadian and United States Governments joined together in a broader defensive alliance, the North Atlantic Treaty Organization. This regional defence association within the terms of the UN Charter was a product of the growing world tension brought about by recognition of the aggressive designs of the Soviet Union. Both Governments recognized that defence base on narrow continentalism no longer made sense. North America was not to be made secure solely by its own efforts and the lines of defence went far beyond geographical limitations. One of the first organizational steps taken by the NATO alliance was to establish Regional Planning Groups to develop and recommend plans for the defence of the various regions of the NATO area. One of those which was established was the Canada-United States Regional Planning Group, which continues in existence today and has responsibility for developing and recommending to higher NATO military authorities plans for the defence of the Canada-United States region.

With the rapid technological advances in the late 1940’s and early 50’s, the air threat to North American became increasingly a matter of concern to the Canadian and United States Governments. The vulnerability of the continent to attack from the air involving perhaps the use of atomic weapons caused the Canadian and United States Governments to give increasing attention to the search for an air defence system against the possibility of a surprise air attack by the Soviet Union. The first major agreements with respect to the continental early warning system came in the years 1951-55.

By the "Pinetree" agreement of August 1951, the Canadian and United States Governments agreed to the extension of the continental radar defence system. This coast-to-coast system was placed in the settled areas of Canada just north of the international boundary. In 1953 agreement was reached on an experimental programme known as "Project Counterchange", a programme which was to grow into the Distant Early Warning Line, which itself was established under an exchange of notes of May 1955. The original agreement in 1953 also made provision for the establishment of a Joint Canada-United States Military Study Group designated by the Chiefs of Staff of each country and with responsibility to study those aspects of the North American air defence system in general and the early warning system in particular which were of mutual concern to the two countries. The Military Study Group was to be advised by the joint scientific team, whose primary task was to carry out such operational research and other scientific studies as might be required. In 1954 the Canadian Government’s decision to construct and operate another coast-to-coast early warning line (the Mid-Canada Line) generally along the 55th parallel was recorded in an exchange of notes with the United States Government.

In the course of 1954, the two Governments issued three joint statements describing the concepts which embraced the work which was proceeding on specific elements of the early warning system. The statements emphasized that what was being developed was a comprehensive, jointly-operated system of warning of the approach of hostile aircraft and for the control of interceptor aircraft. In developing the complete system, the policy has been followed of building outward from likely target areas. The statements described what were to be the main elements of the warning and control system, namely the Pinetree network, the Mid-Canada Line, the DEW Line and the seaward extension of these lines on both flanks of the continent. The Minister of National Defence re-emphasized these ideas in a public statement in 1955 when he spoke of the complete radar network in the following terms: "The Mid-Canada Line will form part of a vast, costly and extensive continental air defence system planned and developed jointly by ourselves and the United States for the better protection of us all. The system is for the benefit of both countries and it is only due to the accident of geography that most of the installation must of necessity be on Canadian soil. Its purpose is for the joint defence of both countries and indeed for the defence of NATO as well – just as much so as anything being done in Europe itself. That is why Canada and the United States have planned and undertaken the project jointly".

While these agreements established the main framework of air defence cooperation between Canada and the United States, they were by no means the only important defence agreements between the two Governments in this period. Between 1951 and 1953 a number of important recommendations were made by the Permanent Joint Board on Defence and accepted by the two Governments, setting out principles governing the operation of both Canadian and United States service aircraft across the international boundary. The principles of interception established in these recommendations became part of the Canada-United States Emergency Air Defence Plan. This Plan provided for operational cooperation between the two air defence forces throughout the last eight years and, as modified by developments arising out of the establishment of the North American Air Defence Command of 1957, will probably continue to do so.

In the same period, i.e., 1950-57, a number of specific and highly classified agreements were completed establishing principles of political consultation between the Canadian and United States Governments relative to their joint defence of the continent. These agreements naturally were consistent with similar commitments for consultation which both Governments assumed within the broader framework of the North Atlantic Treaty Organization.

The principles of defence cooperation agreed to in 1947 continued to be basic to the negotiation of the multitude of specific defence agreements, which were made between the two governments. In implementing these principles of defence cooperation, the Canadian Government took the position that the granting of permanent rights in connection with United States defence installations on Canadian soil was undesirable. Apart from the special arrangements prevailing at the leased bases in Newfoundland, which were inherited from earlier United States-United Kingdom agreements, assurances of tenure for United States service personnel at defence establishments in Canada were limited to specific periods of time. Aside from the question of tenure, Canada-United States defence agreements since 1950, broadly speaking, have included the following important provisions:

[a] – reciprocity;

[b] – retention by the Canadian government of title to any land acquired for joint Canada United States defence installations in Canada;

[c] – the application of Canadian law in all instances; and

[d] – the requirement that detailed information pertaining to all United States defence projects in Canada be provided to the Canadian Government.

Other important provisions, e.g., those concerning construction and the procurement of electronic equipment have been included in Canada-United States defence agreements although their nature has varied somewhat from agreement to agreement. A study of the important defence agreements in the period from 1950 is important to a proper understanding of the basic principles which govern Canadian cooperation with the United States in continental defence. These agreements are not, of course, limited to the air defence field alone.

One of the most important developments in recent years affecting the cooperation between the two Governments in air defence measures began with the instructions given by the two Chiefs of Staff organizations in the summer of 1956 to the Joint Canada-United States Military Study Group. As a result of these instructions, the Eighth Report of the Canada-United States Military Study Group on the "Integration of Operational Control of the Continental Air Defences of Canada and the United States in Peacetime" was submitted to the Chiefs of Staff organizations in December 1956. The Report recommended that the two Chiefs of Staff organizations take action to secure the approval of the Canadian and United States Governments for the integration of the operational control of Canadian and United States air defences in accordance with the concepts outlined in the Report. On August 1, 1957, in a joint announcement by the Minister of National Defence of Canada and the Secretary of Defense of the United States, the agreement of the two Governments was noted for integration of operational control of the air defence forces in the continental United States, Alaska and Canada under an integrated Command responsible to the Chiefs of Staff of both countries. The announcement indicated that an integrated headquarters would be established and that procedures would be worked out in peacetime ready for immediate use in the case of emergency. The integrated headquarters of the North American Air Defence Command (NORAD) became operational on September 12, 1957 on an interim basis. At the time of this writing (February 28, 1958) , the inter-governmental exchange of notes with respect to the permanent establishment of NORAD has not been completed. Speaking in the House of Commons on December 5, 1957, the Minister of National Defence said in part: "In order to improve the capabilities of the air defence forces of Canada and the United States to support the collective security of NATO and thereby provide a greater deterrent to war, the air defence of North America is now considered as a single problem. ….The air defence systems of this continent have recently been completely integrated by the establishment of a joint headquarters at Colorado Springs, with the United States Commander and a Canadian Deputy. The importance to the NATO Alliance of the United States Strategic Air Command nuclear retaliatory forces and the industrial capacity of Canada and the United States makes it imperative that the most effective and efficient defence system be provided. This joint Canada-United States headquarters known as NORAD has been organized on principles that were devised and which operated satisfactorily during World War II for joint and combined commands.

The forgoing provides a summary of some of the more important recent developments in Canada-United States defence relationships as they have affected air defence primarily. It is by no means a comprehensive account of Canada-United States defence cooperation; nor should it be read as a complete account of agreements affecting air defence. For such a complete account, reference would have to be made to many other defence agreements and understandings which have been reached between the Canadian and United States Governments.

All of the principles which have been mentioned in this paper are important. In the air defence field, however, if one had to chose the most important development in Canadian and United States thinking over the past eight years, one could with some assurance argue that it was the relocation by the two Governments that the defence of North America was to be considered as a single problem. Behind this agreed concept are the facts of geography and the potential threat. Both governments support, together with their NATO allies, the principle of the strategic deterrent and recognize that the destruction of this deterrent, which is largely based in North America, would be a first priority for an aggressor. One of the most likely avenues of attack, if it is to come, will be the shortest transpolar route between the Soviet Union and targets in the continental heartland. These strategic facts have no doubt been responsible to a large degree in leading the two Governments to agree on the necessity for an integrated air defence such as that which will be directed by the recently-formed North American Air Defence Command.


This paper was written on 28 February, 1958. There is no detail indicating who wrote the paper. A copy was obtained from the National Archives of Canada July 1998 – for use on the Pinetree Line web site.