Complex sentence: He attended the local schools and then entered the University of Minnesota Law School, but dropped out during World War I to enlist in the U.S. Army, serving as a second lieutenant in a field artillery battery.
Split into simpler sentences: He attended the local schools and then entered the University of Minnesota Law School. However, he dropped out during World War I to enlist in the U.S. Army, serving as a second lieutenant in a field artillery battery.