“It is our true policy to steer clear of permanent alliance with any portion of the foreign world.” George Washington, President of the United States.
I think WW1 was the beginning of the hell the last 100 years have become.
Carving up the Middle East has been a mess ever since.
The Crusades never seem to end.
The Greek invasion of Anatolia turned into a disaster, leading to large numbers of Greek Orthodox residents having to flee to Greece. Some of them were Turkish speakers but if they were Greek Orthodox by religion they were Greeks. I think only the Greeks in Constantinople were allowed to remain in Turkey.
Lenin promised Germany all those lands if thesewsy let him return to Moscow and overthrow the regime, and the Kaiser agreed because that way he would only have a one front war, which he thought he could win before the Americans troops were ready for battle.
Which led to the “stab in the back,” Hitler, and WWII. Also Japan joining the other side because of the embarrassment at Versailles.
By no means full list!
The Europe after WWI was very unstable, there were many communists uprisings and, since the borders were in flux, several local border conflicts.
There were several Polish-German wars and uprisings in Great Polonia and Silesia. (1919-1922)
Hungarian communist coup resulted in Romanian and Czechoslovakian forces fighting and eventually defeating Hungarian Communists (1919).
There was even short, but bloody Czech-Polish war!
Italy was in constant civil unrest, which culminated in Fascist Mussolini coup 1922.
French and Belgian forces were in small scale conflict with Germany since the end of WWI. The most notable was when they invaded and occupied Ruhr land 1923-1925.
Communists (under the Soviet influence) attempted coups pretty much in all European countries, strikes and street fights were common, and even the Bavarian, Hungarian and Slovak Soviet states were proclaimed, but quickly defeated.