Complex sentence: Throughout the war, the Allies had made use of a number of different varieties of amphibious vehicle; in particular, the Ford GPA, a modified version of the Ford GPW Jeep (also known as a "Seep").
Split into simpler sentences: Throughout the war, the Allies made use of a number of different varieties of amphibious vehicle. One of the more commonly used was the Ford GPA, a modified version of the Ford GPW Jeep (also known as a "Seep").