In the upcoming years, Lawrence fought in the royal army in the war against Austria. He participated in the Battle of the Leitha River on 15 June 1246, where Frederick the Quarrelsome was killed. King Béla personally experienced and witnessed his boldness, according to his above-mentioned royal charter. He also took part in a campaign against Austria in 1250, when Béla made a plundering raid into Austria and Styria in the summer of 1250, in retaliation of a former Austrian incursion into Hungary. Lawrence was present during the sieges of Kirchschlag, Parduch and Zrinhous in the period between 1250 and 1253, when Béla launched a campaign against Moravia.