Romania
Operation Margarethe II was the planned German invasion of Romania should the Romanian government decide to surrender to the Soviets. The Romanians did surrender in 1944, but Operation Margarethe II was never implemented. It is worth noting that Hitler had much better relations with Romanian leader Ion Antonescu than with Hungarian leader Miklos Horthy, which might have reduced the need or apparent need for a Nazi invasion of Romania.
Read more about this topic: Operation Margarethe