Unfortunately, there's a number of cold war examples of this. The clearest one is the Iran-Iraq war, but I'd also highlight the ChadianโLibyan war, the USSR invasion of Czechoslovakia, the Gulf War, and the Falklands War.
But trying to take over an entire neighboring country by force so flagrantly, just to expand your borders, this is exactly the kind of shit the UN was built to prevent because it leads to world wars. If it turns out to be unenforceable, the future will look very bad