It’s the number one killer of American troops in Iraq: roadside bombs.
The massive roadside bomb that killed 14 Marines Wednesday flipped their 37-ton vehicle on its top and blew it some 40 feet down the road.
Tonight, there’s disturbing information that some of the most sophisticated of these deadly weapons are reportedly coming from Iran.
U.S. military and intelligence officials tell NBC News that American soldiers intercepted a large shipment of high explosives, smuggled into northeastern Iraq from Iran only last week.
The officials say the shipment contained dozens of "shaped charges" manufactured recently. Shaped charges are especially lethal because they’re designed to concentrate and direct a more powerful blast into a small area.
“They’ll go right through a very heavily armored vehicle like an M1-A1 tank from one side right out the other side,” says retired U.S. Army General Barry McCaffrey.
Military officials say there’s only one use for shaped charges — to kill American forces — and insurgents started using them in Iraq with deadly effectiveness three months ago.
Intelligence officials believe the high-explosives were shipped into Iraq by the Iranian Revolutionary guard or the terrorist group Hezbollah, but are convinced it could not have happened without the full consent of the Iranian government.
And Thursday, Defense Secretary Rumsfeld accused Iran of attempting to derail the democratic process in Iraq.
Iran’s Shiite government has also struck up a seemingly strange alliance with Sunni insurgents to try to drive the American military out of Iraq.
"They are desperate to get us out of Iraq” says Michael Ledeen, author of "The War Against the Terror Masters" and resident scholar in the Freedom Chair at the American Enterprise Institute. “If we succeed in Iraq they will be surrounded by elected governments.”
Military officials acknowledge that these explosives are only the tip of the iceberg... and predict the deadly bombings in Iraq are far from over.