As I map progressively into the heart of Europe, the size of the regions progressively get smaller ... especially as we near the Holy Roman Empire. While Slavonia and Bosnia are part of the Ottoman Empire, Croatia is part of the slim kingdom of Hungary, which in the 17th century acts as a bulwark (note the thicker border). The Ottomans will cross this frontier once more in 1683, but in 1650 their attentions are elsewhere. Croatia stands because Christian Slavonia is far less controlled than Islamic Bosnia; nonetheless, the area on both sides of the border is fairly peaceful.
The 1683 advance did pass through parts of Slavonia, and Agram to the west, but as the movement was on such a broad front there's no specific marching route we can name.
For the record, the river at the top is the Drava, while the Sava is on the bottom.