Complex sentence: In 1740, Moravia was invaded by Prussian forces under Frederick the Great, Olomouc was forced to surrender on the 27th of December 1741, a few months later Prussians were repelled, mainly because of their unsuccessful siege of Brno in 1742.
Split into simpler sentences: In 1740, Moravia was invaded by Prussian forces under Frederick the Great, and Olomouc was forced to surrender on the 27th of December 1741. A few months later the Prussians were repelled, mainly because of their unsuccessful siege of Brno in 1742.