Complex sentence: Pershing abandoned his forward stations south of Namiquipa, concentrating his forces on El Valle, about halfway between Namiquipa and Dublán and sent the 10th and 11th Cavalry back to Colonia Dublán on May 19th to protect the line of communications with Columbus.
Split into simpler sentences: Pershing abandoned his forward stations, concentrating his forces on El Valle, about halfway between Namiquipa and Dublán. The 10th and 11th Cavalry returned to Colonia Dublán on May 19th to protect the line of communications with Columbus.