ARNOLD AIR FORCE BASE, Tenn.-In the early 1940s, an M4 Sherman tank trundled along a trail in the woods at the U.S. Army's Camp Forrest near Tullahoma, Tenn.
As the tank neared a narrow spot, a plume of red smoke spewed from a training mine on one side of the trail, indicating the war machine was "dead." Soldiers spring out in ambush.
The training mine was not the only one near the tank, but it was the only one triggered that day. The others remained behind.
One of them turned up in September 2009, when a security officer walking on a recreational trail at what's now the Arnold Engineering Development Center found what military folks call "unexploded ordnance."
It was identified as a practice tank mine from World War II maneuvers.
Since 2004, ordnance left behind in training maneuvers and firing range practice on U.S. military bases has been targeted by the U.S. Department of Defense's Military Munitions Response Program.
Hundreds of acres at Arnold have already been cleared of old ordnance, but officials say they were surprised by the discovery of a practice mine on the base's 18.5 miles of recreational trails.
Arnold officials say the area is used by hikers, mountain bikers, hunters and outdoor enthusiasts at the base and from local communities.
Property where dangerous military relics might remain is posted with warning signs, officials said.
Most of the recreation trails now have been cleared after their official cleanup began in January, Arnold official Denny Timmons said. A sweep of a small section of trails will be completed next week, he said.
Officials declined to speculate about how many pieces of old ordnance might lie undiscovered. Fewer than two dozen have been found in the vicinity of the trails.
The object the security officer found was a 1940s-era M1B1 anti-tank training mine. It was propped against an oak tree along a 70-year-old tank trail, Timmons said.
Timmons speculated that the tree was a mere sapling when the training mine was buried beside it. As the tree grew, the mine was probably pushed out of the ground.
Arnold officials say the mines were used between 1941 and 1944 for training maneuvers. The camp existed between 1941 and 1946 and records state that as many as 70,000 troops participated in the maneuvers.
U.S. Army Maj. Gen. George Patton's Fort Benning-based 2nd Armored "Hell on Wheels" Division participated in maneuvers at Camp Forrest, but Timmons and others said it there's no way to know for sure if the mines they've been finding were left behind from Patton's training.
It is likely but not certain, Timmons said. Patton's men trained all over Middle Tennessee and his troops were often housed at Camp Forrest or took leave there, he said.
RELICS GO BOOM
Locating and disposing of dangerous historical artifacts has been a big part of Timmons' job since the U.S. Air Force started the Military Munitions Response Program.
Five areas at Arnold were targeted for cleanup.
Officials used a map of Camp Forrest from the 1940s and a modern map of the base to help pinpoint suspicious areas, but the recreation trails area - known as the Camp Forrest Maneuvers Area - was not included, he said.
The discovery in 2009 came after earlier assessments were performed on other areas of the base, officials said. Further exploration was funded after the discovery, and a sweep of the trails in a 2,000-acre chunk of the tract will be completed next week.
Even though the mines are for training, the fuse that fires the smoke charge could cause injury, Timmons said.
After the first mine turned up in 2009, Timmons went to the spot and radioed his coordinates. He couldn't get a signal for his GPS device, so he stepped away a few feet to an opening in the forest canopy.
When he relayed the coordinates he was told, "Well, you may as well get that coordinate there because you're standing right next to another one," Timmons laughed, pointing to a hole in the ground on the other side of the two tank-track ruts.
Timmons called in experts to deal with the dangerous artifacts.
The firm Bay West Inc., a contractor that specializes in clearing munitions, did a sweep that located seven more training mines. That was enough to order the clearing of the trails and the land 100 feet to each side, he said.
RESULTS AND FUTURE PLANS
Bay West site manager Dave Egbert said 19 practice mines, most with no fuse or smoke filler, have been found in the trails area so far.
Egbert said if munitions appear too dangerous to move, they are blown up in place by a team from Eglin Air Force Base near Pensacola, Fla. Seven inert mines are stored in a fenced area on the base.
Egbert and Timmons said a separate sweep will resume this spring on a 514-acre plot known as the "Old Impact Area South," a former firing range that is closed to hunting and has no recreational trails, officials said.
Last year's search of about half that area produced 35 items classified as unexploded ordnance, Timmons said.
When the work resumes this spring, team members will walk side by side over each one-acre grid square to make sure no potentially dangerous pieces of history are overlooked, he said.