Hello, your question about the real power of Serbia in Yugoslavia is very complex. It is complex because there are many circumstances that influenced it. In the first Yugoslavia (1919-1943), ie the Kingdom of Yugoslavia, Serbia is like a state that united all southern Slavs and created that Yugoslavia had many advantages.The king was a Serb (the king was the former king of Serbia), most of the ministers were Serbs and the state was more or less centralized.However, other nations also had privileges.For example, the capital of Croatia , Zagreb was modernized and a smaller tax was paid by the Croats and a large part of the factories was transferred to Zagreb. In 1939, the Croats also received a banovina (something like an autonomous province) that included today's Croatia and Herzegovina. It can be said to Yugoslavia that the Serbs were more influential, but other nations were not without some power in the state, but I think it is justified that the Serbs had stronger power because they died and fight for that state. During the war and the disappearance of the kingdom, Josip Broz Tito came to power and seduced the communist regime. Since Tito was a Croat, Croats had much more power in Communist Yugoslavia than in the Kingdom. Most of the factories were transferred from Belgrade, and those factories were the most important for the development of Serbia itself. The reason for the relocation was due to the "threat of a Soviet attack", because Tito expected an attack from either Hungary or Romania at the time of the quarrel with Stalin. Perhaps this was the main reason, but why he did not return the factories? As for Aleksandar Ranković, he was a strong centralist in the 1960s, he advocated a more central Yugoslavia and he was one of the few Serbs who were close to Tito. On the other hand, there was Edvard Kardelj, a federalist, who demanded as much autonomy for republics as possible. Tito took Kardelj's side and fired Rankovic for alleged "wiretapping" (which was later proven not to have happened). Rankovic would then go to house arrest until the end of his life. Then the famous constitution from 1974 came on the scene, which gave the republics the greatest possible autonomy, but also gave Serbia two autonomous provinces of Kosovo and Vojvodina, the status and power that the provinces had was practically the level of a republic. Serbia could not pass a constitution without the permission of the provinces. This status of the provinces will lead the new president of Serbia, Slobodan Milosevic, to revoke that status. It will anger Croatia and Slovenia to declare independence for fear of a strong Serbia in Yugoslavia.One quote that would describe this situation in second Yugoslavia:"Weak Serbia-Strong Yugoslavia".Although Serbia agreed after the Second World War to be with the Croats who committed the worst genocide against Serbs in this part of Europe. This is my opinion, I tried to be as objective as possible, sorry for a couple of spelling mistakes and greetings.