The Syrian army and its allies made a sudden advance on Feb. 26 into areas held by the Islamic State in northwest Syria, a war monitor said, Reuters reported. The army took the town of Tadef, just south of al-Bab after Islamic State fighters withdrew from it Feb. 23. Earlier this month, a Russian official said Tadef marked an agreed dividing line between the Syrian army and the Turkey-backed forces in the region. The advance has extended Syrian army control across 14 villages and brought it within 25 kilometers (15 miles) of Lake Assad, the stretch of the Euphrates River above the Tabqa dam. Many Islamic State holdings in northwest Syria have been seized in advances by three different, rival forces: U.S.-backed Syrian Kurdish groups, Turkey-backed rebels and the Syrian army. By taking Islamic State territory south of al-Bab, the Syrian army is preventing a possible move by Turkey and its rebel groups to expand southward, and is moving closer to regaining control of water supplies for Aleppo. Turkey's entry into Syria's civil war was intended to push the Islamic State from the border and to stop Kurdish expansion.