|An even better example would be the American Civil War. If there had been a UN back then, they would have been all over the US with "peacekeepers". And, to be fair, they would have sharply reduced the death toll in the years 1860-65.
But at what price? Neither side would have been allowed to win the war, instead the Union and the Confederacy would have been forced to attend interminable "negotiations" which in all probability would still be going on today - and this divided US would not be a super-power.
A real example of this is Cypress. The Cypress "issue" was resolved in a practical sense in the early 1970s. But the UN, by refusing to accept that the war was over, insisting on calling it a "temporary" solution and putting in Peacekeepers who eliminated the practical need for the sides to renew working together, albeit in a new configuration, have successfully prolonged the crisis now for 30 years and into the forseeable future. The UN troops on Cypress aren't "peacekeepers" they are "state-of-war keepers"!