Romania entered WWII as a German ally (November 1940), switched sides after King Michael's coup (August 23, 1944), and fought alongside Soviets to war's end. Its military engagements and territorial treaties reflect this dramatic reversal.
Romania contributed the 3rd and 4th Armies (~200,000 men) guarding German 6th Army's flanks. Operation Uranus (Nov 1942) shattered them—~70,000 killed/wounded/captured. Catastrophic loss; ended offensive capability.
Romanian units supported German 9th Army's northern pincer. Limited engagement; overall German failure. Further depleted Romanian armor/infantry.
Soviet 2nd/3rd Ukrainian Fronts crushed German 6th Army and Romanian 3rd/4th Armies in Moldova. Decisive Soviet victory; triggered King Michael's coup (Aug 23), Romania's switch to Allies.
German attempt to seize Bucharest post-coup (Operation Maximilian). Romanian forces, now Allied, resisted with Soviet support. Germans withdrew; Romania secured.
Romanian armies fought in Transylvania, Hungary, Czechoslovakia (Prague Offensive). ~540,000 served on Allied side; ~160,000 casualties.
Romania ceded Southern Dobruja (Cadrilater) to Bulgaria under German/Italian arbitration. Population exchange followed.
Germany/Italy arbitrated: Northern Transylvania to Hungary; Southern Transylvania remained Romanian. (Trianon 1920 gave all Transylvania to Romania.)
Armistice with USSR/UK/US: Romania restored 1940 borders (except Northern Transylvania returned, Southern Dobruja kept by Bulgaria), paid $300M reparations, accepted Soviet occupation. Paris Treaty (1947) confirmed.
Romania's surrender to Central Powers. Nullified by Versailles. Irrelevant to WWII.
Romania's WWII experience: catastrophic Eastern Front losses, territorial dismemberment (1940), dramatic 1944 realignment, heavy fighting on Allied side, post-war Soviet domination. The treaties reflect great-power arbitrations; the battles reflect a medium power caught between giants.