When Romania switched sides during WW2, did fighting break out amongst the former allies?

by LogicGav

And if so, are there specific examples?

Did Romanian and German soldiers sharing quarters suddenly begin fighting each other?

Did the news of the switch come as a surprise to all involved?

What was the relationship like between the Soviet Army and the new allied Romanian Army? Were there reprisals carried out against the Romanian soldiers for Stalingrad?

RomanianDOC

After Marshall Antonescu, the military dictator of Romania, has been dismissed and arrested by King Michael of Romania in the afternoon of the 23rd August 1944, the German Luftwaffe heavily bombarded Bucharest between 24 and 26 August, especially targeting symbolical institutions like the Royal Palace, The National Theatre, The Romanian Athenaeum, Museums and other important civilian institutions. This gave the new Romanian government the international legal reason to declare war on Nazi Germany.

The German troops in Bucharest - about 8000 men - immediately attempted to seize Bucharest, but were repelled by the city's defences under General Iosif Teodorescu, Military Commander of the Capital, who opposed to the Germans two army corps, led by generals Constantin Constantin and Gheorghe Rozin.

Romanian troops liquidated the German resistance points inside the capital. Heavy fighting took place on the Splaiul Independentei (at the Luftwaffe General Staff for the Balkans), at the Superior War School (where the German Military Mission for the Army of the Land was located), in Rahova, Cotroceni, as well as in the northern area, in Baneasa, Pipera and Otopeni. The German forces withdraw, on the night of August 27/28, 1944, but were captured the next day by the troops of the 4th Army, in Gherghita (25 km from Ploieşti).

The successful operations of the Romanian army allowed that, on the arrival of the Soviet troops in Bucharest on August 30, the city was completely liberated of the German troops.

Other Wehrmacht units in the country suffered severe losses: Romanian units attacked German garrisons at the Ploiești oilfields, forcing them to retreat to Hungary. The Romanian Army captured over 50,000 German prisoners around this time, who were later surrendered to the Soviets.

You can find some hints here: Third Axis Fourth Ally: Romanian Armed Forces in the European War, 1941–1945, by Mark Axworthy, Cornel Scafeş and Cristian Crăciunoiu

In early September, Soviet and Romanian forces entered Transylvania and captured the towns of Brașov and Sibiu while advancing toward the Mureș River. Their main objective was the regional capital Cluj. However, the Second Hungarian Army was present in the region, and together with the Eighth German Army engaged the Allied forces on 5 September in what was to become the Battle of Turda, which lasted until 8 October and resulted in heavy casualties for both sides. The Hungarian Army carried out its last independent offensive action of the war, penetrating Arad County in western Romania. Despite initial success, a number of ad-hoc Romanian cadet battalions managed to stop the Hungarian advance at the Battle of Păuliș, and soon a combined Romanian-Soviet counterattack overwhelmed the Hungarians, who gave ground and evacuated Arad itself on 21 September.

Beside the Romanian territory, the Romanian Army fought against the Wehrmacht alongside the Red Army in Hungary, Yugoslavia, Austria and Czechoslovakia, from August 1944 until the end of the war in Europe. In May 1945, the First and Fourth armies took part in the Prague Offensive. The Romanian Army incurred 126,000 casualties fighting Nazi Germany. Of some 538,000 Romanian soldiers who fought against the Axis in 1944–45, some 167,000 were killed, wounded or went missing.