Complex sentence: The 2nd Mounted Artillery Battalion lost almost 30% of men, the 21st Regiment-almost 25%; the 12th Uhlans Regiment that was used as a reserve lost 5 officers and 216 men, both killed and wounded.
Split into simpler sentences: The 2nd Mounted Artillery Battalion lost almost 30% of men, the 21st Regiment-almost 25%. The 12th Uhlans Regiment that was used as a reserve lost five officers and 216 men, both killed and wounded.