With all respect, keeping the peace by inserting lightly armed tripwire forces - from relatively powerful nations - in between warring factions has enjoyed on and off popularity for about 2,000 years. Canadian peacekeeping, in the Pearsonian tradition might be traced to the Russian expedition of 1919.
The first UN peacekeeping mission (UNMOGIP) was mounted in 1949, and it is still running. That was long before Lester Pearson 'invented' peacekeeping.
If anyone 'invented' modern UN peacekeeping it was Sir Brian Urquhart.
In 1956 the Brits, the French and the Israelis tried a bit of imperialistic bullying which infuriated President Eisenhower and threatened the foundations of the emerging liberal; democratic Western consensus. Several senior officials, including Mike Pearson, from several countries - all working under Urquhart's general guidance - developed the idea of a United Nations Emergency Force (UNEF), a step up from UNMOGIP and, arguably, a step back in time. The key players, including Eisenhower, Eden and St. Laurent, for Canada, agreed the basic thrust of the thing: a way to save Anglo-French face while giving Nasser what he had just stolen, fair and square as Teddy Roosevelt said of the Panama Canal.
There was one huge obstacle: the UN General Assembly; many, many (maybe even most) members, led by the USSR, wanted the Brits and French to be left dangling and to be punished, diplomatically, at least, for their effrontery. A resolution had to be crafted and sold, country-by-country, while the hard-liners were kept in the dark. Mike Pearson was one of the most accomplished diplomats in the room: a hard nosed and skillful negotiator who was widely admired and trusted for his integrity and skill. He wrote the key resolution and then shepherded it through the General Assembly until he had a working majority.
It may not seem very exciting but, for days and days the tensions in New York (and Washington, Moscow, London, Paris, Cairo and Ottawa, too) were high - dangerously high. Nuclear forces were on heightened alert. Pearson worked tirelessly, day and night, mostly in the shadows, persuading, begging and cajoling and modifying the proposal (which may, in it original form, have owed more to Louis St. Laurent than to any one other person) until the UNEF, which deployed in 56, was developed. One of the key elements in achieving success was Pearson's ability to offer Canadian troops, Canadian leadership and Canadian money to the project. St. Laurent's cabinet had given Pearson a virtual catre blanche - more than almost any foreign minister has ever carried into negotiations.
Pearson earned all the accolades and the Nobel Prize, too. But neither he, nor Canada, 'invented' peacekeeping.
(I was told, years later, by someone who was very near the Egyptian centre that Nasser was furious; he felt Pearson had cheated him our of a chance to humiliate the Anglo-French leadership and, by so doing, to add immensely to his prestige and power in the new non-aligned movement. That's why he objected, at the last minute, to the Canadian infantry battalion: from The Queens Own Rifles of Canada - because they were 'too British.' It was designed to rob Pearson of some of his 'glory.')
As a couple of by-the-bys:
"¢ The first handbooks for UNEF were two little, hip-pocket sized, pre WWII British War Office pamphlets (sh!t house readers, we used to call them) called Keeping the Peace, Part I and Part II -= they were, later and over and over, expanded and republished until they became great thick (and, consequently useless) Canadian volumes;
"¢ LGen (Ret'd) ELM "tommyâ ? Burns (who had commander 1 CDN Corps in WWII) was hauled out of retirement to be the first UNEF Commander and he vindicated old MGen Middleton by being concerned, first and last, with full dress and feathers;
"¢ The decision to replace the QORofC battalion with 'housekeeping' troops set the Canadian Forces on a destructive path in which combat support and combat service support troops were badly depleted to meet successive UN mission requirements and then combat arms units were required to cough up 'volunteers' to refill e.g. Signals.