This one was only made possible after war was fought 100 years prior
This one came about as the final straw in the British Empire's back that was started off by the American Revolution.
https://en.wikipedia.org/wiki/Dissolution_of_the_Soviet_Union
This one was was caused by the USSR suffering multiple setbacks after its war in Afghanistan, multiple proxy wars (e.g., Six-Day War and the Yom Kippur War; the Angolan Civil War; Somalia and Etheopia; Nigerian Civil War; etc.), putting down attempts at reform in the eastern bloc (Praque Spring the Polish Crisis), the massive unrest that had plain-clothes secret-police beating protesters just before the Berlin Wall fell, a violent revolution in Romania, and the August Coup failed.
I thought you were making the point that they were peaceful , and I was refuting that stuff was peaceful.