 Complete the following phrase:  After the death of Algirdas in 1377, Andrei, as the eldest son, rivaled his half-brother Jogaila, whom Algirdas had designated as his heir. Jogaila at the time enjoyed strong support from his uncle Kęstutis. Andrei organized an anti-Lithuanian coalition with Polotsk, Grand Duchy of Moscow, and the Livonian Order. In 1379, Moscows army attacked eastern territories of the Grand Duchy; Moscow and Lithuania were at peace since the Treaty of Lyubutsk in 1372. Andreis brother Dymitr I Starszy did not defend the Principality of Trubetsk and Starodub. However, the Russian army did not remain in taken territories and retreated back to Moscow; Andrei and Dymitr followed it. Jogaila signed a ten-year truce with the Teutonic Knights on September 29, 1379 and a truce with the Livonian Order on February 27, 1380, thus fracturing the coalition. He further enlisted Mamai, a powerful warlord of the Golden Horde, and Oleg II of Ryazan as his allies against Andrei. In 1380, Andrei and Dymitr fought for Moscow in the 