Best indications are that companies raised by Major Gilbert in late 1863 formed part of Nixon's Tennessee Cavalry Regt. Companies that can be identified were raised along the Tennessee-Alabama line. The Major of the orginal regiment is not known.
If Major Gilbert had a mounted organization under his command during the period Nov 1863 - Oct 1864, it does not appear in the records. An inspection report made in Oct 1864 by Capt Wm M Hammond, A A G of Roddey's Cavalry, doesn't list Major Gilbert. He could have raised an unreported independent command during the winter of 1864/1865.