Complex sentence: Upon arrival on June 13, he was one of four assigned to Fort Sam Houston Army Ground & Services Redistribution Station and sent home for 30 days of recuperation, with permission to travel anywhere within the United States during that period.
Split into simpler sentences: Upon arrival on June 13, he was one of four who were assigned to Fort Sam Houston Army Ground & Services Redistribution Station. All four were sent home for 30 days of recuperation, with permission to travel anywhere within the United States during that period.