CALLOW, BRAVE AND TRUE, A Gospel of Civil War Youth by Jay S. Hoar, Thomas Publications, 267 pages, paperback $20.

Today, we would no more think of allowing children to serve in the armed forces than we would contemplate sending our octogenarians off to Marine Corps boot camp in preparation for World War III. But that hasn’t always been the case, surprising though that fact may be to many readers.

In our saddest war of all — the War Between The States — the boy soldier was not that much of an anomaly. Civil War drummer boys, valets and orderlies were often mere children who grew up quickly, no strangers to the ravages of war. The author, a Civil War buff and professor at the University of Maine, Farmington, has written previously about the older veterans of that tragic war. He now tackles the subject of the youngest.

And young they were, by any standards. A Maine lad, 10-year-old James E. Powell II of “Hangtown,” a section of The Forks Plantation in Somerset County, was for a brief time the youngest ever to serve in the Civil War.

Actually, young Jimmy left Maine for the military life with his father, Lt. James Powell, when he was only 5 years old, accompanying his dad to duty stations in Tennessee, Arkansas, Texas and Indian Territory. He was barely 8 years old when he began serving his father in an official status as valet-waiter.

When Fort Sumter’s bombardment greeted the dawn of Apr. 12, 186l, young Powell had served in that capacity for two years and thus has the distinction of being the first of the youngest Civil War soldiers to be on duty — 10 years, 9 months, 13 days. He held the honor barely a week, however, being displaced by Thomas L.F. Hubler, a drummer boy of the 12th Indiana Infantry, whose Civil War service began at age 9 years and 7 months.

When his father was killed at Shiloh, Jimmy, 11, homeless and grief-stricken, found his military career ended. Friends of his late father saw to it that he got back to his family at The Forks through the assistance of Gov. Israel Washburn. Powell died there on June 29, 1929, one day before his 79th birthday, and was laid to rest in the family plot.

Jimmy Powell’s story is only one of nearly 50 biographical essays about the child soldiers of the Civil War that Hoar has amassed in this extensively researched book. Two of these child soldiers were only 6 1/2 years old at the time of enlistment. Lists of the youngest to earn the Medal of Honor, the youngest to serve, soldier boy casualties, and the latest born veterans are among those appended.

“I try to write only about things that others have not written about,” Hoar said in a recent telephone conversation. In his latest effort he seems to have held to that criteria, and as a result “Callow, Brave and True” deserves a place in any serious collection of Civil War lore.