Complex sentence: He claimed 5 victories in Spain, the majority of his victories of World War II were claimed over the Eastern Front, with 20 over the Western Front, including two victories flying the Messerschmitt Me 262 jet fighter and one four-engined bomber.
Split into simpler sentences: He claimed 5 victories in Spain, and the majority of his victories of World War II were claimed over the Eastern Front. He also claimed 20 victories over the Western Front, including two victories flying the Messerschmitt Me 262 jet fighter and one four-engined bomber.