You know that old joke about how the “Holy Roman Empire” was neither holy, nor Roman, nor an empire? Well, speaking as a history pedant, that joke would be better if it were told about the 1683-1699 Great Turkish War. I mean, the Holy Roman Empire may not have been especially holy (although that’s subjective), and it wasn’t Roman, but it was an empire. The Great Turkish War, on the other hand, wasn’t great (also subjective, but it definitely wasn’t so great if you were in the Ottoman army), wasn’t “Turkish” (Turkish nationalism was still more than a century away), and it wasn’t a war, it was actually a series of them. Several European nations, including the Holy Roman Empire (which at the time was controlled by the Austrian Habsburgs), Hungary (also controlled by the Austrian Habsburgs), Croatia (ditto), the Polish-Lithuanian Commonwealth, Russia, Venice, and a bunch of smaller partners all joined a new Holy League at the behest of Pope Innocent XI (d. 1689), and the Ottomans managed to entangle themselves in conflicts with each of them–the Venetians in Greece, the Russians in Crimea and at Azov, the Poles in Moldavia, and the Austrians in Austria. This would have been a tough fight for the Ottomans to have won at their peak–and by the 1680s, they were no longer at their peak, though they were still a force.
We’ve already mentioned a couple of the crucial battles of the Great Turkish War–the Battle of Vienna in 1683 kicked the conflict off and made for a pretty wrong-footed start from the Ottoman perspective, and the Battle of Mohács in 1687 cost the Ottomans a huge chunk of territory in eastern Europe. Those two battles, plus the Battle of Zenta in 1697, plus the loss of Azov to Russia, were the major engagements of the war, and all went against the Ottomans. The result was the Treaty of Karlowitz, adopted on January 26, 1699, after two months of negotiations in the Habsburg town of the same name (the modern Serbian town of Sremski Karlovci). Karlowitz wasn’t a turning point in European history–the war was the turning point–but it does mark a milestone in the course of both European and Ottoman history, as it was the first treaty that the Ottomans were forced to conclude on European terms.
The Ottomans were forced to give up considerable European provinces to the Habsburgs, territory that includes parts of modern Hungary, Serbia, Croatia, and Bosnia-Herzegovina. They lost Dalmatia (another part of modern Croatia) and the Peloponnese (in Greece) to Venice (though they got the Peloponnese back not long after), and parts of modern Ukraine and Moldova to Poland-Lithuania. Negotiations begun here and concluded in the Treaty of Constantinople (1700) ceded Azov to Russia (the Ottomans later got that back as well). But the symbolism of Karlowitz, the unambiguous acknowledgement that the power dynamic in the Ottoman-Europe relationship had leveled out or even shifted a bit toward the European side, was arguably more important than its tangible terms.
It’s common outside of Ottoman specialists to talk about the “decline” of the Ottoman Empire starting all the way back in the 16th century and fully manifesting with the Treaty of Karlowitz. Among Ottoman specialists, however, the “decline theory” has been pretty well debunked. It’s kind of silly, if you think about it, to posit an almost 400 year long decline phase.
The Ottoman Empire looks weaker in the 17th century than it was in the 16th century not so much because it was in decline but because the rest of the Mediterranean was catching up. Yes, the empire struggled through a string of sultans, and even the occasional grand vizier, who weren’t exactly dynamic leaders–a decision in the mid 16th century to keep prospective heirs to the throne confined to the palace rather than out governing provinces and getting experience is usually blamed for this–but the imperial bureaucracy was so well-entrenched by this point that the machine of state hummed along regardless. What we see in this period more than a decline is a transformation of the empire into something that looks more like a modern bureaucratic state than the absolutist empire it had been previously. But as I say, the rest of the neighborhood was starting to catch up, and get smart, and the Ottoman defeat in the Great Turkish War shows, among other things, that the Ottomans weren’t able to fight a multiple front war against multiple European enemies, but it doesn’t really show that the empire was swirling the drain.