Think Baghdad, and the thought of mass casualty explosions caused by vehicle-borne improvised explosive devices -- VBIEDs -- comes to mind. But obscured by the smoke and flame of al-Qaida's favorite weapon is a smaller device specifically used for assassination or intimidation of Iraqis cooperating with U.S. forces.

The weapon is a "sticky bomb," an easily concealable explosive device attached to a vehicle with magnets and detonated by either a timer or a remote controlled device, such as a cell phone.

"The only way to combat them is for people to watch their cars and also check their vehicles every day," said Capt. Ryan Chlebek, an intelligence officer with the 1st Battalion, 68th Armor Regiment, which operates in the Adhamiya district of eastern Baghdad.

The sticky bomb has been in use for months. Al-Qaida is believed to be behind their use. The largest bombs so far have only packed about 15 pounds of explosive power. Some are smaller and appear more for intimidation than murder. U.S. officials estimate 50 to 60 have gone off over the past six or seven months in Baghdad. In the Adhamiya District, the number is six to eight since mid-summer.

To raise awareness of the sticky bombs, U.S. forces now hand out boxes of informational leaflets in Arabic at Iraqi Security Force checkpoints for passing on to motorists. Police, troops and Sons of Iraq personnel at checkpoints now conduct random undercarriage searches of vehicles.

Baghdad's Adhamiya district -- about 50 square kilometers and with about 2 million people -- is a particularly restive area of the city since the toppling of Saddam Hussein by U.S. forces in 2003. Its eastern sectors include predominantly Shiite areas such as Shaab, Beida and Hayy Ur, which are close to Sadr City, the Shiite slum and powerbase for anti-American cleric Moqtada Sadr and his now officially disbanded Jaish al-Mahdi gunmen and Iranian-influenced "Special Groups."

Adhamiya's western reaches include Waziriyah and Magrib, mixed sectarian areas, and Old Adhamiya, a predominantly Sunni area from where al-Qaida terrorists still operate.

Statistics provided by 1-68 show the difference in explosive-device activity in the two sectors. From August to November there were no VBIEDs in the eastern sector until a car bomb exploded outside a school in the Beida/Shaab sector. In the Western sector, there were only two VBIEDs in 90 days before the explosions of two weeks ago shattered the calm.

There were only six IEDs -- improvised explosive devices -- in 1-68's sector over the past 90 days. Four were on the demarcation line between the battalion's battle space and that of another unit closer to Sadr City. In the western sector there were 37 -- nearly one every three days.

Officers of 1-68 say the targets of the bombs are Iraqi Security Forces and the SOI rather than American troops, which have generally become targets of opportunity.

The so-called sticky bombs -- think of WW-II naval limpet mines -- are the latest in the series of explosive devices AQI terrorists and other extremists have used in the Iraq conflict. First came the IEDs -- many made with hundreds of pounds of explosives left over from Iraqi army war ordnance that wreaked havoc on U.S. troops, resulting in the Pentagon equipping Humvees, the utility vehicle meant to replace the Jeep, with heavy armor, and later equipping troops with armored mine resistant vehicles such as the Caiman and International for transport and patrolling.

Terrorists then began employing EFPs -- explosively formed penetrators -- which shoot out a molten copper disk that penetrates armor. The United States has accused Iran of supplying EFPs to Shiite extremists. VBIEDs, suicide vests and IRAMs -- basically a line-of-site fired, flying IED, are also in the mix.

Capt. Ray Maralfonso, another intelligence officer with 1-68, said the use of sticky bombs for assassination shouldn't be surprising

"We think it's AQI-affiliated," he said. "They're trying to stir up the pot. Basically, it's typical insurgency -- trying to cause confusion, chaos and fear."

Confusion, chaos and fear -- the basic ingredients of terror are known all to well to Iraq's people. For months violence in Iraq, and especially Baghdad, has been on the decline because of the success of the U.S. troop "surge" strategy put in place late last year and increasing Iraqi Security Force capabilities.

The sudden spate of VBIEDs last week may have been coincidence or a sign al-Qaida had obtained more explosives. But perhaps they were a precursor of an increase in bombings as Iraq approaches provincial elections in late January. If that's the case, incidents involving sticky bombs could rise as well.