In a satanic race to the depths of depravity against their evil sidekicks, the Shia militias and al-Qaeda-suspected Sunni insurgents have now begun to use what the Iraqis are calling "dirty weapons."  

Dirty weapons? Try chemical weapons. The chlorine gas the insurgents are unleashing on Iraqi streets are even categorized as a weapon of mass destruction if used in large quantities. Just think of World War I.

Considering his use of chemical weapons against the Iranians (during the Iran-Iraq war) and his own people (during his reign of terror), Saddam Hussein must be pleased from the grave, indeed, with his charges.

Taking a page from Saddam's vile playbook, the use of chemicals is just the latest effort by the insurgents to sow death and destruction in Iraq - not to mention to rattle Washington's already shaky political will for the war.

Just last week, in the second and third chemical attacks in a month, insurgents blew up trucks filled with potentially deadly chlorine gas, leaving multitudes sickened.

"That's just another way they're trying to adapt to cause some sort of chaos here in country," said Army Lt. Gen. Raymond Odierno, the deputy commander in Iraq.

Last Tuesday, six people died and at least 150 were wounded or overcome by fumes when a chlorine tanker truck exploded. The next day, five were killed, sending over 50 to the hospital when a pickup truck laden with gas cylinders was lit off.

A U.S. military raid near Fallujah last week probably averted more attacks, finding chlorine gas cylinders, propane tanks, fertilizer (for use as an explosive), chemicals, munitions plus a truck and three additional cars being turned into "bombs on wheels."

While the attacks were lethal, the chlorine gas appears to have been less than effective. The explosions killed people, but the blast's heat probably burned off most of the toxic chlorine gas.

It's probable the insurgents will figure this out, too, leading to the question: What's next in the insurgent's little shop of horrors?

Watching the anguishing congressional deliberations and the already heated 2008 presidential races, the Sunni insurgents must be plotting their next malevolent move to achieve their ultimate objective: Ignominious American defeat and withdrawal.

The Shia militias have their strategy. They're going to ground - or heading to Iran like Shia cleric Moqtada al Sadr - while the security crackdown in Baghdad is under way, only to indubitably resurface when the coast is clear.

Al-Qaeda is targeting American dominance of the skies by ambushing helicopters in a tactic borrowed directly from the mujahedeen's successful anti-air campaign against the Soviet Union in Afghanistan in the 1980s.

Army Maj. Gen. William Caldwell, the military's spokesman in Iraq, called the gas attacks, "a real crude attempt to raise the terror level by taking and mixing ordinary chemicals with explosive devices."

If he's right about the terrorizing effect, we'll likely see more yellowish green chlorine gas clouds in the days to come - or other types of chemical attacks.

Chlorine is a good tool for terror. First, it's a prevalent industrial chemical. Plus, it's a choking agent, causing panic.

Depending on exposure levels, chlorine will irritate eyes and skin and cause a victim's lungs to swell, fill with liquid or even dissolve, leading to asphyxiation.

We could also see other choking agents such as phosgene, another common manufacturing chemical. (Phosgene caused 80 percent of the over 1 million chemical casualties during World War I.)

Fortunately, choking agents disperse rapidly in open air and act slowly, allowing potential victims to take countermeasures or depart the affected area.

On the downside, if the insurgents are encouraged by their initial chemical attacks, they might also move to something more complex like mustard gas, a deadly blistering agent which can be made from common chemicals.

The suicide bomber and the car bomb remain the deadliest terrorist weapons in Iraq, but chemical weapons are being added to the mix, escalating the conflict and adding to the importance of defeating the insurgency.

And as Congress considers revoking the president's authority to wage war in Iraq, they should be mindful that we're on a mission to destroy a monstrous enemy almost without comparison in its disdain for human life.

Peter Brookes is a columnist forThe New York Post, a Heritage Foundation senior fellow and author of "A Devil's Triangle: Terrorism, WMD and Rogue States."