Complex sentence: The Meuse-Argonne Offensive was the largest in United States military history, involving 1.2 million American soldiers, and was one of a series of Allied attacks known as the Hundred Days Offensive, which brought the war to an end.
Split into simpler sentences: The Meuse-Argonne Offensive was the largest in United States military history, involving 1.2 million American soldiers. It was one of a series of Allied attacks known as the Hundred Days Offensive, which brought the war to an end.