This is a feeble response off the wall because I can not find any info about Holbrook's Maryland Battery. Taking a wild shot, I suggest you like into Latrobe's Maryland Battery as it served in East Tennessee in 1862 and in early 1863 went to Mississippi. Capt. Rowan also commanded this battery. No mention of Holbrook. More info would be helpful. The index for all 128 volumes of the Civil War are little help as they do have Holbrook listed in index but no first name which is also not provided in your post. More info please
Ron