The Citadel in Quebec City, built a century and a half ago to help repel American attacks that never came, stands as a reminder that U.S.-Canadian relations were not always as cordial as they are today. But when President Reagan and Canadian Prime Minister Brian Mulroney hold some of their summit sessions at that stone fortress starting Sunday, they will be reinforcing the bonds that their two countries share as well as trying to resolve some of the differences.
The two leaders plan to sign an agreement to modernize the Distant Early Warning line, the DEW line. The new North Warning System is designed to provide a more complete radar link in the two countries' defenses against attack across the polar region. In return for its contributions to installation costs, Canada hopes to get a share of the construction contracts.
Reagan and Mulroney will also concentrate on U.S.-Canada trade, which exceeded $105 billion last year. Canada is far and away America's leading trading partner, surpassing Japan or the entire European Economic Community. After a period of defensiveness about U.S. investment in Canada, Mulroney has said clearly that "Canada is open for business again."
But there are areas of disagreement. Foremost is the question of how urgently action is needed on acid rain, the airborne pollution that is killing Northern U.S. and Canadian lakes and forests. Many experts believe that the principal sources of the deadly pollutants are auto and electric-power-station exhaust fumes that are carried in the atmosphere and return to Earth in rain or snow.