Look at a terrain map of the Balkans. With Italy, you at least have usable coastal highways that let you theoretically push forward no matter where you land [1]

Look at a terrain map of the Balkans. With Italy, you at least have usable coastal highways that let you theoretically push forward no matter where you land [1], but the Balkans don't really have any coast-to-interior routes that can support a large force, and they don't offer that much worth capturing. [1] But there's so few of them and the chokepoints so obvious that it's relatively easy to defend them.