More significant, however, was the distance between the two men on a matter of policy: what U.S. forces are obliged to do if they happen upon inhumane treatment of prisoners or civilians by the Iraqi forces they are training to take over the security mission in Iraq.
It was a brief moment, but highlights an important difference between the uniformed military and their civilian leaders, a sharp line that has gotten muddied since the September 11 terrorist attacks.
"Obviously, the United States does not have a responsibility when a sovereign country engages in something" we disapprove of, said Rumsfeld.
Pace, a Marine, demurred.
"It is absolutely the responsibility of every U.S. service member, if they see inhumane treatment being conducted, to intervene to stop it," he said.
Rumsfeld attempted to correct him.
"But I don't think you mean they have an obligation to physically stop it; it's to report it," he said, turning to face Pace at the podium.
Pace stood his ground, schooling the defense secretary in both the policy in Iraq and the moral obligation the military believes it has no matter where it is deployed.
"If they are physically present when inhumane treatment is taking place, sir, they have an obligation to try to stop it," Pace said.
An aide to Pace said Wednesday the brief disagreement did not affect or reflect the men's working relationship. But officers in Iraq and the Pentagon took heart in what they saw from the new chairman: someone willing to state out loud what the U.S. military stands for and aspires to, even if it contradicts his boss.
"It was a very important response from Gen. Pace, and also managed to highlight a chasm between him and the secretary," an Army officer training security forces in Iraq said by e-mail.
U.S. service members in Iraq are trying to instill not just discipline and tactics into the 210,000 troops and police officers recruited so far, but also a code of ethics and honor not previously associated with Iraq's security apparatus. If the police and troops are to win the good will of the people -- and set Iraq on a course for democracy -- they need to foreswear brutality.
It's not easy. Iraq has a violent history. Many Iraqis believe the only way the country will be pacified is with a strongman leader, though hopefully not quite as ruthless as Saddam, and are willing to accept what excesses come along with it. Already there have been multiple incidents of abuse, illegal imprisonment, inhumane treatment and in some cases torture at the hands of those in the employ of the Interior Mministry and to a lesser extent the Defense Ministry.
Their American trainers are empowered to stop it when they see it. Pace made that clear. Whatever the legal sticking points of sovereignty -- officially the U.S. military is in Iraq at the invitation of the government, although it is not subject to its laws -- the U.S. military feels a moral and professional obligation to protect the helpless.
More important to these officers beyond the practicality of setting a good example for Iraqi trainees, Pace expressed what the vast majority in the military believe and what they want to hear their leadership loudly proclaim: They are on the side of good, and are expected to behave like it.
That message has gotten murky in the last few years as the White House and Pentagon grappled with new boundaries for the treatment of prisoners held in the war on terror.
The Abu Ghraib prison abuse scandal -- a disgrace military officers reject as an aberration born of lack of discipline and bad leadership -- made it possible not just to believe the worst about U.S. forces but to envision it in four colors. They have been battling perceptions ever since though, interestingly, less so in Iraq where prisoners prefer being held in American jails rather than Iraqi.
As the prison scandal unfolded, multiple memos were released that showed the White House had reinterpreted law and policy to allow the harsh treatment of military prisoners. A 55-page draft Pentagon memo detailed legal defenses soldiers could use if, in following the new guidelines, they were subsequently charged with torture.
One military interrogator, asked in 2003 for a wish list of techniques to use against prisoners in Iraq, rejected the request: "It comes down to standards of right and wrong -- something we cannot just put aside when we find it inconvenient. Bottom Line: We are American soldiers, heirs of a long tradition of staying on the high ground. We need to stay there."
And it was the judge advocates general, uniformed military lawyers, who said "no" to the White House. They dissented strongly from a March 14, 2003, memo written by then Deputy Assistant Attorney General John Yoo entitled "Military Interrogation of Alien Unlawful Combatants."
The officers were overruled. For six months the memo was the controlling legal authority for the treatment of detainees, superceding even the Geneva Conventions which otherwise stipulate how combatants are to be treated in war.
More recently, President Bush has threatened to veto a defense bill if it came to him with Senate-approved language prohibiting U.S. government officials from engaging in torture, cruel or inhumane treatment.
"Why does it take the United States Senate to stand up and say we are against torture?" a senior military officer complained recently. "We have to reclaim our moral authority."