When the Mediterranean Triad was preparing for battle against the German Army, something surprising happened: the Germans did not initially attack South Slavia, but instead took advantage of seizing Vienna to head directly south into Hungary.
Indeed, the Germans had attacked Hungary without declaring war.
But considering the situation, it was not surprising since Germany had attacked many countries without declaration, and Hungary was not an exception.
It's worth mentioning that Hungary's area was still vast, almost encompassing the entire Hungarian Plain, including Transylvania, which Romania coveted.
From this, one could discern the purpose of the German's invasion of Hungary: to firmly tie Romania to their war chariot.
Why did Germany place such importance on this small Balkan country, Romania?
Because Romania possessed the petroleum resources desperately needed by Germany, which were absolutely irreplaceable treasures for both Germany and Italy.