Complex sentence: McLean was a retired major in the Virginia militia; but at 47, he was too old to return to active duty at the outbreak of the Civil War; he made his living during the war as a sugar broker supplying the Confederate States Army.
Split into simpler sentences: McLean was a retired major in the Virginia militia, but at 47, he was too old to return to active duty at the outbreak of the Civil War. He made his living during the war as a sugar broker supplying the Confederate States Army.