Complex sentence: Initially, Russia used aviation only for reconnaissance and coordination of artillery fire, but in December 1914 a squadron of Ilya Muromets bombers was formed and used against the German and Austro-Hungarian armies.
Split into simpler sentences: Initially, Russia used aviation only for reconnaissance and coordination of artillery fire. In December 1914 a squadron of Ilya Muromets bombers was formed and used against the German and Austro-Hungarian armies.