Great powers have fought for centuries for influence in the territory known today as Syria, each seeing a prize in its strategic position, stretching from the Mediterranean Sea to the Euphrates River and beyond. That struggle continues today.

In Syria’s 13-year civil war, Iran, Russia and the Lebanese militant group Hezbollah backed the brutal regime of President Bashar al-Assad, while the United States, Turkey and other countries backed various rebel groups.

Now, after a lightning advance by rebels and the rapid-fire collapse of Mr. al-Assad’s government, great powers — albeit with different ones in ascendence — are jockeying for advantage within Syria’s borders. For the first time in years, the skies are empty of Syrian and Russian bombers — but airstrikes by Israel, Turkey and the United States continue.

Here is a look at the foreign countries that have been present in Syria — often operating through local allies — and what they stand to gain and lose from the end of the Assad regime.