heartland of Ottoman empire was in Anatolia not in the Balkans!
Please give/list your source?
As already has been said, Anatolia was just where the Turkish peasants lived. It hadn't been the heartland of the Ottoman empire since Timurlane's time (in large part because of Timurlane's invasion). And in any case, the Ottoman empire may have started as a "Turkish" empire but it certainly wasn't very Turkish by 1800. (Though the loss of most of the heartlands in the 19th Century meant it was more Turkish in 1900.)
As to sources, pretty much any half decent history of the Ottoman empire will illustrate where the political and economic power was. I would recommend the two volume "Economic & Social History of the Ottoman Empire" from the Cambridge University Press.
Or potentially having Turks and other groups move to Ukraine, which had been so depopulated by the Crimean Tartars on their slave raids.
The Ottomans didn't have enough people to settle all of the land they already held. Settling people in the Ukraine could only come at the cost of more established regions and the taxes those regions supplied... And there's no way the Ottomans are taking the Ukraine with a post 1900 PoD! Not if the Ottoman leadership is halfway sensible!
I have read before that the people of the Balkans were referred to a state sheep at times, as the Ottomans had no desire to convert them when they could instead charge them extra taxes and take their children as slaves. If perhaps there had been more of a Muslim population in the region there would have been a greater chance to...
Well, the Ottomans had no problem making their Muslim subjects pay Christian-only taxes. While being a member of the ruling class was for Muslims only, for peasants and ordinary city-dwellers, there wasn't a whole lot of difference. The real downside of trying to convert their Christian subjects was that it would cause unrest, and that wasn't good for business. And I am not sure that a greater Muslim preponderance in the Balkan population would have made much of a difference. Egypt was pretty solidly Muslim (more than 80% Muslim at that time), but that didn't stop it from being torn away.
Also the Ottomans wasn’t really integrated into the European intelligentsia, some Ottoman citizens was, but these also happened to be second class citizens. Try to compare the cultural output from the Ottomans and Russians in 18-19th century which are widely known in the West today. The Russians produced work of literature still admired today, they was famous for their ballets. The Ottomans...
Yeah. I don't think either side was terribly interested in the cultural output of the other.
Why was the Balkans the heartland? Aren't the western Levant and Mesopotamia also densely populated?
And if keeping the Balkans is nessecary, would it have been possible to Islamize the Balkans more? Like, set up certain industries in Rumelia and subsidize muslims to go live and work there?
The Balkans were the heartland because that's where the population density was highest, the forests most abundant and the lands most fertile. And no, the Levant and Mesopotamia were not densely populated. Ottoman Syria (a larger region than the modern country of Syria because the French and British cut the pie as they saw fit in 1919) wasn't the poorest region of the empire on a per capita basis, but population was sparse. Mesopotamia was a complete backwater, was severely underpopulated and may have been the poorest province in the empire. The Ottomans were a Mediterranean empire, so Iraq was poorly connected to the rest of the empire and being subject to regular Persian invasions for 200 years had done it no favours. By 1900, improvements in security from the 18th Century lows, successful efforts to force nomadic groups to settle, investment in agriculture (there were for example some very successful royal estates in Mesopotamia formed in the 19th Century that would in the last years of Ottoman rule provide much of the income for the royal family) and the construction of the Suez canal meant Mesopotamia had started to recover, but in 1914 it was still a very poor region.
And the Ottomans did set up industries in the Balkans. They of course lost these as they kept losing wars to their Christian neighbours and being obliged to allow nationalist revolts to succeed.
As for subsidizing migration for Muslims, well, the Ottomans did settle refugees coming from the lands the Russians had taken from them in the Balkans. These people would then have to move again (if they hadn't died in the chaos and violence of the independence wars) when the areas they'd settled in were taken by vengeful nationalists. Resettling from Muslims from the Asian side of the empire wouldn't have been terribly practical since there was no excess population to move anyways. And as I say to Clandango above, I don't think the Balkans having a Muslim majority would have helped much anyway.
How did Japan become so developed even before the industrialization?
Because Japan didn't have any major wars or plagues for centuries and the Tokugawa Shogunate was very effective at governing.
Japan is a very rare example of a region that stood on the brink of a deforestation crisis and was successfully pulled back from the brink. That the Tokugawa managed to do that is honestly pretty bloomin' amazing.
Japan was never entirely isolated. Western science books were imported through Decima the entire period from 1641 to 1853, and there was a permanent school of translators sponsored by the shogun. It is not my impression that the Ottoman Empire had such schools. Translations in this period were mostly unique occasions.
I am not sure how the Ottoman institutions would compare to the Japanese ones. Certainly they did have the Palace School for the training of the civil service, and their civil service was well supplied with translators. So far as I am aware, I don't think the Ottoman government was ever especially interested in science and technical books (not during the early 19th Century when Japan was still in the Tokugawa period). They tended to prefer hiring foreign advisers.
It perhaps bears saying that when I said that the Ottomans were very open to innovations, that's not to say that they were more open than Japan was. Rather, they were more open compared to other non-Western states, a field in which both they and Japan were leaders.
fasquardon