Iraq’s parliament this month passed a new de-Baathification bill, which awaits only expected approval by the five-member presidency council before becoming law. Much remains to be done, but this is an important step toward political reconciliation — and it further strengthens the case for America to remain committed to its crucial mission in Iraq in the months and years ahead.

During Saddam Hussein’s day, if you wanted a professional job in Iraq you basically had to join the Baath Party. For most of the 1 million-plus who did so, this hardly implied direct involvement or even complicity in crimes of the state. Hussein was so paranoid that only his very inner circles were entrusted with information on the dictator’s plans and policies.

Appropriately, the new legislation will punish only former Baathists who were in the three highest circles of the former regime’s power structure. That probably amounts to a few thousand people. Others will generally be allowed to rejoin Iraqi society, regain their access to jobs and federal pensions where available, and avoid prosecution for previous crimes of the state. Under earlier rules, dating to edicts issued by Paul Bremer during his early weeks as Iraq’s administrator in 2003, the four highest circles had been effectively ostracized. This meant tens of thousands of individuals were directly affected — and hundreds of thousands indirectly, including family members. That precluded many of Iraq’s most talented professionals and politicians from helping rebuild their nation — and it created widespread bitterness among Sunnis, who constituted the bulk of Baathist Party members, that the current Shiite-led government would never accord them fair rights in the new Iraq.

The legislation is imperfect, of course. Most notably, the law could keep all former Baathists out of Iraq’s security and legal institutions. While understandable as a way to alleviate Shiite worries about a possible Baathist-Sunni resurgence, this goes too far. Taken literally, it would interfere with efforts to bring Sunni volunteers into Iraq’s security forces (unless waivers are issued). This possible problem will have to be cleared up. But if that happens, a major step will have been taken toward building sectarian trust.

The reformed de-Baathification legislation is one of half a dozen key political issues codified into American law last year by President Bush and Congress as “benchmarks” we expected Iraqi leaders to address. Other matters so identified are hydrocarbon legislation; a provincial powers act (clarifying the roles of Iraq’s 18 provinces vis-a-vis the central government); a provincial election law to facilitate the next round of local elections; a process for holding a referendum on the political future of Kirkuk, the disputed northern oil city (and for compensating individual property holders and sectarian groups who lose out in such a vote); and a more transparent and trustworthy process for purging sectarian extremists from positions of government authority.

These benchmarks are reasonable goals. It is regrettable that insufficient progress has been made on the others (with the exception of the long, slow progress of purging extremists from official positions). What really matters, however, is that Iraqis come to view themselves as a single people working together to build a new nation, and address their inevitable differences legislatively rather than violently. As such, to the extent that benchmarks are employed, we would advocate using a longer list — and include Baghdad’s sharing of oil revenue with the provinces, the hiring of Sunni volunteers into the security forces and into the civilian arms of government, improvements in the legal and penal systems, and, over time, reform of the electoral system to weaken the role of the sectarian parties. In all but the last of these considerable progress has been made in the past year.

This political progress resulted from a year’s worth of substantial effort to reduce violence in Iraq. Proponents of the surge always said that getting violence under control was an essential prerequisite to reconciliation, not the other way around. The full surge has been in place and operating for just over six months, and already violence has fallen dramatically across the country. The achievement in such a short time of significant legislation that requires all sides to accept risk and compromise with people they had been fighting only a few months ago is remarkable. It would have been unattainable without the change in strategy and addition of American forces that helped bring the violence down.

The progress of the past year also required American political pressure. The ongoing engagement of Ambassador Ryan Crocker, Gen. David Petraeus and others in cajoling and compelling Iraqi political leaders into making compromises across sectarian lines has been crucial — not only in passing the reformed de-Baathification law but in purging Shiite extremists from government and persuading Prime Minister Nouri al-Maliki to gradually, if begrudgingly, hire Sunni volunteers into the security forces. American politicians of both parties have sometimes applied useful pressure too — when they have made clear that they are focused on Iraq, that they are determined to insist that Iraqi leaders behave responsibly, and that the United States will not underwrite sectarian violence or oppression. But they have acted harmfully when threatening to withdraw U.S. forces rapidly, without regard to conditions, without regard to whether Iraqi leaders are trying to make compromises across sectarian lines.

As Crocker said last spring, “The longer and louder the debate gets, the more danger there is that Iraqis will conclude that we are going,” leading to “a hardening of attitudes” among sectarian factions.” Iraq’s institutions are too weak, and its sectarian wounds still too raw, for us to expect the gains of the past year to endure in the face of a quick and nearly complete American withdrawal.

The number of American forces in Iraq matters. Although the change of U.S. strategy announced last January and the change in attitude among Sunni Arabs were critical to the successes achieved in 2007, the addition of five Army combat brigades and three Marine battalions was also critical. Petraeus and Gen. Ray Odierno know the strains the surge has placed on the military and believe that we can reduce our forces to pre-surge levels by this summer without compromising our gains. Considering the big steps taken by Iraqi security forces over the past year, as well as the tremendous damage our forces and Iraqi forces, together with the Iraqi people, have done to al-Qaeda in Iraq, the Sunni Baathist insurgency, Iranian-backed special groups and the fighting elements of the Jaish al-Mahdi, this belief is probably justified. But we cannot be sure.

Al-Qaeda in Iraq is working hard to regroup, and our soldiers are fighting hard to prevent that. Activities of Iranian-backed special groups continue to be worrisome. And much remains to be done politically at the local and national levels to secure the gains we have made.

Some in Washington are already calling for a commitment to additional reductions, resulting in force levels below pre-surge levels, even before we have finished the current drawdown. Such calls are unwise. America has made this mistake in Iraq before — withdrawing too soon, attempting to hand security responsibilities over to Iraqi forces unable to accept them, and assuming that the best-case scenarios will play out. We must not make that mistake again. It is inappropriate to try to evaluate the possibility of reductions beyond pre-surge levels before we have had time to examine the situation after the completion of that drawdown. Therefore, Congress, the president and the American people should not expect Petraeus to report in March on the feasibility of still further reductions but, rather, on the sustainability of the reductions already in progress.

The strain on the U.S. military is great, and we are all concerned. But sustaining 15 brigades in Iraq for six more months or another year will not break the force. Reducing forces in Iraq too rapidly, however, even by one or two brigades, might seriously jeopardize the tenuous success we are seeing. We should not take that risk.