Complex sentence: Dana went through the Vicksburg Campaign and was at the Battle of Chickamauga and the Third Battle of Chattanooga, and urged the placing of General Grant in supreme command of all the armies in the field, which happened in March 1864.
Split into simpler sentences: Dana went through the Vicksburg Campaign and was at the Battle of Chickamauga and the Third Battle of Chattanooga. He urged placing General Grant in supreme command of all the armies in the field, which happened in March 1864.