On 15 June 1961, the premier of the Soviet Union, Nikita Khrushchev, gave notice to the Western powers of his government's intention to conclude a peace treaty with East Germany in six months. He asserted the position that once the Soviet Union had made peace with Germany the occupying powers would no longer have any justification to retain their garrisons in Berlin. The other three occupying powers – Britain, France, and the United States – and the North Atlantic Treaty Organization (NATO) disagreed, of course, and various contingency plans were put in place. On 13 August, Soviet forces completed the construction of the Berlin Wall. The steady flow of refugees from East Germany to West Germany through Berlin had become a large embarrassment, and the wall was intended to stop this exodus. Some analysts have criticized the Western occupying forces in Berlin for not taking decisive action the moment that construction on the wall began. They argue that the Soviets later backed down in the face of determined opposition during the Cuban Missile Crisis of October 1962 and would have done the same in regard to the Berlin Wall. No such move was made, however, and the wall became a permanent feature that largely stopped the flow of East Germans seeking the freedom and prosperity of the west.On 7 September, Prime Minister John Diefenbaker announced to the House of Commons and the public that Canada's response would be to increase the ceiling of its armed forces from 120,000 to 135,000. The addition of 1,106 troops and another 1,515 that were to be available as immediate reinforcements from Canada brought the NATO brigade, 4 CIBG, very close to its full wartime establishment. As a further measure, the planned rotation of 1st Battalion, The Black Watch from Germany would be delayed until 1962. (Newly rotated units take time to adjust to local conditions and become fully operational.)
The crisis eventually petered out in October after a standoff between U.S. and Soviet tanks in the streets of Berlin. The episode demonstrated that the Soviets were not prepared to push the situation to the logical conclusion: outright nuclear warfare. In some regards, however, the Berlin Crisis never really came to an end. Rather, the crisis simply evolved into a new phase in which the Soviet Union attempted to break out of what it perceived as encirclement by the NATO countries. Confronted by an alliance that had nuclear weapons positioned from western Europe to Turkey, the Soviets attempted a "tit for tat," placing missiles in Cuba within easy range of the United States. This event precipitated the Cuban Missile Crisis.
Canada meanwhile embarked on a steady upgrading of the military capabilities of its NATO brigade group. In 1962, the brigade reconnaissance squadron's 21 Ferret scout cars were augmented with the addition of a troop of nine CH112 Nomad scout helicopters. Previously, in late 1961, the Honest John nuclear artillery of 1st Surface-to-Surface Missile Battery was introduced. French-made Entac and SS11 anti-tank wire-guided missiles were procured and an anti-tank company was added to 4 CMBG in 1964 (B Company, 3e Battalion Le Royal 22e Régiment, which had become the divisional anti-tank battalion). These acquisitions, however, were but the tip of the iceberg.
But the most important step was the conversion of the brigade into a completely mechanized formation with all fighting soldiers mounted in armoured vehicles. Canada had been trying to develop its own armoured personnel carrier (APC), the Bobcat. Soon after becoming defence minister in 1963, Paul Hellyer announced that the project was cancelled and that Canada would instead be purchasing the U.S.-made M113A1. In 1965, the brigade started receiving these APCs, which included several specialized variants. The arrival of the M113A1 armoured personnel carriers meant that the infantry would now be protected from small arms fire and shrapnel. The infantry also benefited from the firepower provided by the machine gun mounted on each vehicle. In 1968, the artillery exchanged their towed 105mm guns for 155mm M-109 self-propelled howitzers, a transition that offered protection for the crews as well greater range and heavier shell. The brigade was now fully mechanized and equipped with state of the art equipment. It was bigger than an equivalent British brigade, and, in fact, the territory assigned to it in the Emergency Defense Plan was about the same as that given to a British division.