In fact Hitler tried to convince Yougoslavia to join the Axis. By allowing his troops to cross the country and helping him invade Greece , he even promised Yougaslavia an access to the Mediteranean by granting the Greek city of Saloniki to the Yougoslavians. However, as we all know, the Yougaslavian refused. Had this plan succeeded then , not only Hitler would have had another allie but save both invasion and occupation troops+ probably get some more men from Yougoslavia to invade Russia. Could be a nice "what if " topic.

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