The warfare with the Teutonic Order continued from 1345, and in 1348, the Knights defeated the Lithuanians at the Battle of Strėva. Kęstutis requested King Casimir of Poland to mediate with the pope in hopes of converting Lithuania to Christianity, but the result was negative, and Poland took from Lithuania in 1349 the Halych area and some Ruthenian lands further north. Lithuania's situation improved from 1350, when Algirdas formed an alliance with the Principality of Tver. Halych was ceded by Lithuania, which brought peace with Poland in 1352. Secured by those alliances, Algirdas and Kęstutis embarked on the implementation of policies to expand Lithuania's territories further.