The insurgency in Iraq that took root during the American-led invasion and emerged full-blown just weeks after President Bush declared “Mission Accomplished” in May 2003. It became an irrevocable part of the political and military landscape on Aug. 19, 2003, with the bombing of the United Nations headquarters in Baghdad, which killed 22 people, including the chief of mission, Sergio Vieira de Mello.

The bombing was a signature terrorist act, designed to undermine the image of a U.S.-dominated coalition that could transform shock-and-awe military might into a calm and successful postwar management of the public order across the nation. It led quickly to the withdrawal of many of the international officials and non-governmental organizations helping with Iraq’s reconstruction, and all but destroyed the international community’s ability to provide humanitarian aid.

The murder of international civil servants serving under the blue-and-white flag of the United Nations was yet more proof—if any was needed— that in modern conflicts of a terrorist, insurgent or sectarian nature, nothing and nobody is shielded by the internationally recognized laws designed to keep war within agreed limits.

But another image has come to stand just as starkly as an emblem of gross disregard for the laws of armed conflict during the war in Iraq.

Abu Ghraib prison west of Baghdad will forever be a symbol of abusive behavior by American military jailers. Responding to the nascent insurgency, the U.S. military arrested thousands of Iraqis and put them under the control of overstretched and under-trained military police based in Saddam Hussein’s former political prison. Photographs of Army guards smiling, and one giving ‘’thumbs up,’’ as their Iraqi detainees were humiliated, degraded and harmed, came to replace the video of jubilant Iraqis toppling Saddam Hussein’s statue as the most-remembered image of the war.

Although the Bush administration used various arguments in its efforts to rally support for the invasion—Saddam Hussein’s alleged links to al-Qaeda and suspected arsenals of unconventional weapons most prominent among them—the White House statements always carried a patina of international legal rationale: The goal was to punish a tyrant who flouted a series of United Nations resolutions and had been responsible for decades of crimes against humanity in the mass executions and gassing of his own citizens. Thus, while President Bush’s “global war on terror” was the central justification from political Washington, even the war’s earliest critics acknowledged that Saddam Hussein was a wrongdoer who should, at some point, be held to account.

Any examination of the laws of war as applied to Iraq should divide the conflict, much as the military did, into two periods. The first was the build-up to war and the relatively brief period of major combat operations that began with air strikes on Baghdad and tanks breaching the berm in Kuwait, and ended with the capture of Baghdad and the toppling of the Saddam Hussein regime. The second was the lengthy, complicated and bloody fight that pitted coalition forces and a newborn Iraqi government against Sunni insurgents, foreign terrorists and radical Shiite militias—and the effort to quell sectarian conflict between Sunnis and Shiites.

The rush to Baghdad exemplified the modern way America fights wars, with its emphasis on deploying the smallest troop levels possible, and compensating with precision munitions, heavier firepower, more far-reaching communications and an emphasis on refined targeting to limit collateral damage to civilians and civilian infrastructure. “Speed kills,” was the motto of Gen. Tommy R. Franks, the wartime commander, and the rapidly moving offensive certainly proved his doctrine—at least for the goal of capturing Baghdad.

The Iraqi capital fell in less than 30 days, certainly with minimum casualties for coalition forces and limited civilian casualties, as well. And even in advance of the air attacks and ground invasion, the American military dropped leaflets urging Iraqi soldiers to go home and not be killed.

But a strategy nicknamed “Baghdad First,” which called for the military to rapidly sweep past population centers in order to topple the pillars of power in the Iraqi capital, left large swaths of the country completely ungoverned, a vacuum filled by lawlessness and then insurgent and sectarian violence. The pressure from Washington to keep troop levels low, plus decisions to disband the Iraqi army and toss Ba’athist Party members from government jobs, meant that there were too few troops to impose order over an escalating number of disenfranchised, angry and well-armed Iraqis—even though the Fourth Geneva Convention requires occupiers to ensure public order and safety. History will no doubt write that an effective military campaign plan to oust the Saddam Hussein regime foundered on insufficient attention to, and failed efforts at, planning for the post-invasion occupation and stabilization effort.

Even before the regime of Saddam Hussein was driven from power, Ba’athist Party loyalists had scattered throughout the country, and officially sponsored but locally commanded bands of irregulars, called Fedayeen Saddam, harassed American combat troops and lines of supply to dramatic effect.

These forces wore no uniforms with fixed and distinctive insignia; they hid among the population; they did not carry arms openly; they answered to no chain of command that followed the laws of war.
And they were in the vanguard of a changing conflict in which conventional warfare morphed into insurgency vs. counter-insurgency, and then again transformed into sectarian conflict, Sunni vs. Shiite, with all the hallmarks of civil war.

The anti-coalition forces avoided traditional military engagements and instead chose tactics that included the most perfidious ways of fighting: hiding among the civilians, inviting American attacks that would kill and wound innocents; fighting from protected sites; planting roadside bombs targeted at military convoys yet that killed indiscriminately; and car bombings of civilian locations for maximum death, disruption and dismay.

The anti-coalition campaign was designed for mass terrorizing of the population, and so included abductions, torture, and the dumping of bodies to sow fear and disorder and foster yet more rounds of sectarian violence. Insurgents who kidnapped coalition military personnel flagrantly violated the rules protecting prisoners of war established in the Third Geneva Convention.

One technique favored by U.S. adversaries was to fight from within mosques, sites that are protected under international law, in hopes that images of American forces counter-attacking these revered religious locations would stir even greater anger on the Arab street.

The use of religious sites as cover for military actions is in most circumstances a violation of international law and always forfeits their protection, yet coalition forces, as well, were required under those same tenets of international humanitarian law to calibrate their response to what was proportional; in other words, to counter a sniper in a minaret, a commander may not order his forces to shell the entire mosque compound.

The mosque as battleground took a most dramatic turn in February 2006, with the bombing of the Golden Mosque in Samarra, a revered Shiite holy site. In retrospect, the conflict in Iraq clearly morphed on that day from one in which the Sunni insurgency was the greatest threat to stability to one in which the country risked sliding into Sunni vs. Shiite sectarian chaos, and civil war.

The war in Iraq also elevated a new arsenal into the military lexicon, as Improvised Explosive Devices, or IEDs, killed and wounded more American troops than any other weapon. Built from artillery shells, plastic explosives and even flammable liquids, these devices were buried in roadways, hidden inside animal—or even human—carcasses or inside garbage cans, and planted on the undersides of bridges—and then detonated by remote control when military convoys drove past. Massive car bombs also were given a name in this category, VBIEDs, or vehicle-borne improvised explosive devices.

IEDs are designed to inflict the maximum pain, often being packed with shrapnel and nails. Dating back to the Hague Rules of 1907, armies are required to avoid using weapons that cause unnecessary suffering beyond what is required to disable enemy fighters.

In particular within Baghdad, death squads loyal to various sectarian leaders, and some even alleged to be under the control of partisan officials within the various Iraqi ministries, carried out kidnappings and executions. These were in clear violation of Common Article 3 of the Geneva Conventions, which applies during internal conflict or civil war and outlaws “violence to life and person, in particular murder of all kinds, mutilation, cruel treatment and torture.” (It need not be noted that such kidnappings, torture and murder are outlawed by Iraqi domestic laws, even though such behavior against political enemies was a tool of the Saddam Hussein regime while in power, as well.)

As the war dragged on, a series of incidents in which American forces killed Iraqi civilians in questionable circumstances resulted in international anger, and courts martial.

The alleged massacre of Iraqi civilians at Haditha generated global public attention and outrage, and crystallized concerns about the way some American forces interpreted their rules of engagement.

Four United States Marines were charged under the Uniform Code of Military Justice with murder in the killings of 24 Iraqi civilians—at least 10 women and children were among them—in the insurgent-plagued Sunni village of Haditha, northwest of Baghdad, in November of 2005. Another four officers had been charged with dereliction of duty by failing to ensure that the incident was properly reported and investigated.

The shootings that killed two dozen Iraqis, most of them unarmed, occurred after a military convoy was struck by an IED, killing a Marine lance corporal. Over the next several hours, the Marines attacked several homes, killing those inside, including one man in a wheelchair. The Marines also shot men in a taxi at the scene.

The Marines said they were following standard rules of engagement in a hostile area. They said the IED had been detonated by someone in the nearby houses, and that their convoy then had come under fire. Marines said they had spotted a man with a weapon fleeing one of the houses.

Even supporters of the Marines’ actions were hard-pressed to say their behavior did not go well beyond legal norms of proportionality, in which military response cannot be excessive when viewed in light of its expected utility. They may have further violated the law of war by failing to take the required steps to properly identify the target, in particular as grenades were thrown blindly into rooms to clear them of potential adversaries. Therefore, they may have violated the law by not striving to minimize collateral damage.

The treatment of Iraqi detainees captured in sweeps designed to quell the insurgency has left a similar scar on the United States’ reputation.

A high-level, independent panel that reviewed the abuses at Abu Ghraib prison, led by James R. Schlesinger, a former defense secretary, attributed the “acts of brutality and purposeless sadism” to a cascading series of failures that stretched from the prison upward through the chain of command.

The panel called for improvements in the training of military police and intelligence officers, with focus on guaranteeing that behavior remained in keeping with American jurisprudence, approved doctrine of the armed services and the United States’ interpretation of the Geneva Conventions.

Senior Pentagon leaders failed to offer clear guidance on what techniques were allowed for interrogating prisoners, the review found, allowing military jailers and intelligence officers to believe they were allowed to put detainees in stress positions, to use dogs to induce fear and employ other harsh techniques.

Perhaps most significantly, the Schlesinger panel found that the response to the growing and tenacious insurgency in Iraq—employing harsh interrogation techniques in an effort to find “actionable intelligence” to thwart the adversaries—had actually damaged the ability of the United States to obtain intelligence and protect national security.