In 1924 Canadian military officials recognized that armoured warfare would be a major player in wars to come. They also realized two other things. 1) Canada needed home-built tanks to swell national pride show that Canada was a major nation, not just Britain's overseas colony, and 2) that they would need (in conjuction with the regular Tank Corps) an Elite Tank Corps that would be able to handle unconventional situations and that could easily adapt to overcome any obstacle they were faced with (overwhelming enemy forces, superior enemy technology, unsuitable environments, etc). From this idea, they developed Project Beef Stew, a program to collect tallented individuals from all over Canada and groom them to become Canada's first generation of elite tankers.
In 1931, a lack of suitable recruits led to the formation of a second conference wich came to two conclusions. They could shut down the program all together, or they could expand it to include a wider range of individuals. After a vote, the proprosal to expand the search toppled the cancellation proposal by a slight majority of 54%. Thusly, the program was expanded to include any male recruit from ages 17 to 23 of any race, descendance, or religion, as long as they were a Canadian citizen. From here on out the project had no lack of promising recruits. Prejudice was still common but nearly anyone could enlist.
In 1936, the project bought some Vickers Medium Mark II and A9 Cruiser light tanks from Britain. The Canadian engineers modified the suspension on the A9 hull to give it more weight capacity, then proceeded to improve armor protection and add a more powerful engine to deal with the increased weight. It was fitted with a modified Mk II Medium turret, featuring a fully enclosed machine gun cupola above the gunner's position, and an early recoil-reduction system. Finally, the question of armament was posed. Originally a British 2-pdr gun was to be mounted, but military command decided a Canadian-made gun would be more fitting. By May 1937, a suitable 77mm howitzer was designed and began rolling off the production line, and the vehicles weight capacity was again improved to deal with the heavier main gun. Finally, the internal layout was rearranged to seperate the driver's and crew's compartments, and to make room for more rounds of ammunition. When production finally started in 1938, the vehicle weighed in at 20 tons, had 40mm of frontal armor protection, carried 22 77mm HE rounds. Due to a smaller powder charge than later rounds of similar caliber, the 77mm gun had only slightly higher penetration ability than German 57mm AT guns. The tank was christened the Mk. I "Macdonald" Medium Tank.
A unit of 124 Macdonald tanks, crewed by "Beef Stew" tankers, arrived in France in early 1940 to help defend it in case of German invasion. They proved extremely successful agains the German Pz. II's, as their heavier main guns tore through the German Armour. As well, they were tough and rugged, and could easily plow their way through rough terrain unaccessible to similar vehicles. However, the engine had overheating problems, the crew compartment was very hot and stuffy, and there was no coaxial machine gun. Vehicles were withdrawn from frontline units in late 1941 and completely phased out in early 1942.
*I'm not exactly great at this yet, so this is mostly frankensteining DP's work, bear with me though, and hopefully i'll get better.