It's hard to win a war if you quit fighting in the middle. That's the lesson we should learn from Ethiopia's New Year's message to us.

Six months ago, when the militia of the Islamic Courts Union seized the Somali capital of Mogadishu, it appeared that the al-Qaida-affiliated radicals were on the verge of a major triumph. The redoubtable StrategyPage declared them "unstoppable," and the usual hand-wringers were urging us to negotiate with them.

All Islamic extremists are unlovely, but the Islamic Courts Union are a particularly nasty bunch. They modeled themselves on the (now deposed) Taliban in Afghanistan, and imposed their harsh version of Sharia (Islamic law) on the territory they controlled. Movies and the playing of music were banned. So were smoking tobacco and chewing khat, a mild hallucinogen. Women were barred from beaches. People who didn't pray five times a day were threatened with beheading.

More than 20,000 Somalis fled in small boats across the Gulf of Aden to seek sanctuary in Yemen, said the United Nations High Commissioner for Refugees. Thousands more clogged refugee camps in neighboring countries.

In November, the Islamic Courts Union began an offensive against the provincial capital of Baidoa, where the U.N.-recognized government of Somalia had taken refuge, and announced plans to extend its "jihad" to Ethiopia, Somalia's neighbor to the west, and Kenya, its neighbor to the south.

But all that changed in the last week of 2006. A Reuters dispatch Dec. 28 indicates why: "The bloated corpses of Islamist fighters and an unbroken line of tank tracks along the Baidoa-Mogadishu highway tell the story of a swift advance for the Somali government and its Ethiopian allies."

That dispatch was in some ways more politically correct than accurate. Such Somali government forces as there were followed well behind the Ethiopian tanks. Considering how rapidly they fled, to describe the Islamists as "fighters" was excessively kind.

The Islamists swiftly abandoned Mogadishu, but declared they would make a stand at the southeastern port city of Kismayo, but as Ethiopian troops approached on New Year's Eve, the Islamists fled once again without giving battle.

The Islamists hoped to flee into Kenya, but Kenyan troops barred the way. The bulk of the Islamist forces who haven't gone home are thought to be hiding in the forests west of Kismayo, doing their best to avoid the attention of Ethiopian tanks.

Ethiopia won in short order because it unapologetically used force against vicious killers who understand only force. They killed the people they needed to kill without worrying overmuch about collateral damage, and not at all about world opinion. And though the Ethiopian soldiers are Christians, they were hailed as liberators in this overwhelmingly Muslim country.

When, during the march on Baghdad, we unapologetically used force in Iraq, we also had rapid success with minimal casualties. But since the statue of Saddam fell in Firdous Square in April 2003, we've acted as if the war were over. Our focus shifted to peacekeeping and nation-building, though it's hard to be a peacekeeper when there is no peace to keep, and it's hard to rebuild a nation when the bad guys are still out there blowing things up.

We've become a Gulliver bound by our own politically correct strictures. The first battle of Fallujah was called off in April 2004 because Sunni politicians in Iraq's parliament objected. The result was a major propaganda victory for al-Qaida, and a bloodier battle in November 2004.

When Moqtada al Sadr, an Iranian puppet, staged an uprising to coincide with the first battle of Fallujah, he was allowed to remain free, even though he was wanted for the murder of the moderate Shia cleric Majid al Khoie, because the leading Shia cleric, the Ayatollah Ali al Sistani, reportedly insisted upon it. Today, Mr. Sadr's death squads are responsible for most of the sectarian killings in Iraq, and Mr. Sadr is considered the most powerful figure in the country.

President Bush is expected to announce soon a temporary "surge" in U.S. troop levels in Iraq. Troop strength is important. But more important to success is what our troops -- who currently must operate under very restrictive rules of engagement -- are permitted to do.

Half-measures in war typically produce half-baked results. If the military measures we take in Iraq must first be approved by Iraqi politicians and the editorial board of The New York Times, we will not succeed even if we double the number of troops.