Complex sentence: Many Historians debate whether he played a fundamental part in the Seven Years War as arguably, he was an influential figure embarking on reforms for the army such as replacing the musket with the flintlock musket for greater accuracy.
Split into simpler sentences: Many historians debate whether he played a fundamental part in the Seven Years' War. Arguably, he was an influential figure as he embarked on reforms for the army such as replacing the ordinary musket with the flintlock musket for greater accuracy.