Complex sentence: In April 1863, the unit was attached to General Gracie's Brigade and fought in the Battle of Chickamauga, where it suffered heavy losses: 45% of its 902 men; in the 1st Battalion, 169 of 239 soldiers were either killed or wounded.
Split into simpler sentences: In April 1863, the unit was attached to General Gracie's Brigade and fought in the Battle of Chickamauga, where it suffered heavy losses: 45% of its 902 men. In the 1st Battalion alone, 169 of 239 soldiers were either killed or wounded.