Complex sentence: In prewar China, Lilley befriended and played catch with a Japanese soldier, but in 1940, soon after the outbreak of World War II, his family returned to the United States as fighting between Japanese and Chinese forces began to ravage the coastal regions of China.
Split into simpler sentences: In prewar China, Lilley befriended and played catch with a Japanese soldier. But in 1940, soon after the outbreak of World War II, his family returned to the United States as fighting between Japanese and Chinese forces began to ravage the coastal regions of China.