It's not a new weapon on the Iraqi battlefield, but CBS News has learned it's being used more now than ever. And for the first time, the Army has admitted this weapon is killing its soldiers.
Capt. Benjamin Jones, of the U.S. Army's 2nd Brigade, 2nd Infantry Div., led CBS News chief foreign correspondent Lara Logan to the place where he lost a young soldier, Jeremiah Vietch, to one of these hand grenades in June.
"The vehicle was right there, and they had thrown a grenade right over that wall," Jones says, pointing to a barrier.
Pfc. Vietch, 21, of Fort Carson's 2nd Brigade "Warriors," died after the explosive penetrated his armored vehicle in Baghdad's violent Dora neighborhood.
The terrorist group has been eager to take credit for the use of this lethal weapon.
Three months ago, their organization in Iraq announced the creation of a new "Thermal Brigade" and paraded men dressed in black and holding weapons in a video posted on the Internet.
They even used diagrams to show how this Russian-made weapon actually works.
Those diagrams matched military explanations obtained by CBS News: When the pin is pulled and the grenade is thrown, a small parachute is released. It stabilizes the grenade and ensures that it comes down vertically on its target.
The shape charge inside punches through the armor, and slow-burning explosives are released to ensure the deadliest effect.
During the battle in Dora, the Army says more and more of these hand grenades are being used.
In firefights, like the one that suddenly broke out during Logan's visit last week, it's yet another worry for the soldiers.
Capt. Jim Keirsey says the armor-piercing hand grenades were used against his men on a street corner in a massive complex attack that killed five soldiers at the end of July.
In another attack, Staff Sgt. Paul Crenshaw was almost killed by one just a few yards down the road when it was thrown over a wall into his vehicle, wounding him and his gunner.
The soldiers say it's impossible to know when ordinary-looking civilians at the side of the road will suddenly launch their deadly weapons - and that makes attacks like this just about impossible to stop.