After nearly 15 years, federal prosecutors finally harpooned U.S. Islamic terror financing. Earlier this week, prosecutors in Dallas, Texas, obtained 108 convictions against the financiers of international mayhem and murder, who were organized under an outfit called the Holy Land Foundation for Relief and Development, which funneled $12 million to the Hamas Palestinian terror group. The government convicted the foundation and five of its organizers. The prosecutorial Ahabs have been chasing this whale since 1996.

Yet the minutiae of the case are less important than what Americans must take from it: Militant Islam is thriving in America in groups such as the benign-sounding Council on American Islamic Relations, an unindicted co-conspirator in the Hamas funding case. The key organization connected to funding Hamas is the Muslim Brotherhood, whose membership includes the Islamic Society of North America and which founded the Muslim Students Association. The latter group is active on college campuses across the United States.

Prosecutors say the Brotherhood is the parent of Hamas, and, after the convictions in Dallas, former Washington Post foreign correspondent Douglas Farah put that point into focus. The Hamas funding trial showed “the true agenda of the international Muslim Brotherhood and its organizations in the United States — the abolition of the United States government … and support for a designated terrorist organization.”

The Brotherhood is clear about its goals, as one piece of evidence at trial, a Brotherhood memorandum from 1991, demonstrates. A section of that memorandum titled “Understanding the Role of the Muslim Brotherhood in North America” boldly suggests the Islamic conquest of America: “The [brothers] must understand that their work in America is a kind of grand Jihad in eliminating and destroying the Western civilization from within and ‘sabotaging’ its miserable house … so that it is eliminated and God’s religion is made victorious over all other religions.”

Mr. Farah says the memo provides “a clear public record of why these groups were founded and how” and belies the benign façade of such groups as CAIR.

The question, of course, is how the federal government should treat these organizations and how to reform U.S. immigration policy to acknowledge that Islam is incompatible with democratic rule.

As to the first, it means the federal government must shut down the Muslim Brotherhood and its affiliates, seize their assets, then prosecute and/or deport their members. It must also comb the records of these groups to find out who funds them, and, where necessary, again, prosecute and/or deport those moneymen. To the degree that unwitting American citizens, foundations or corporations are subsidizing or supporting these groups, they must stop or face criminal sanctions.

The second point demands iron realism. As foreign affairs writer Srdja Trifkovic has observed, Islam must no longer be treated as a religion but instead as a political ideology that, like communism before it, seeks to overthrow our republic. Koranic exegesis and Islamists who expound it are clear that politics, terror and jihad are the means to impose Islam upon others.

Europeans are learning this now, and the situation there suggests that all immigration from Islamic countries must be stopped, all student and work visas must be cancelled and the government must monitor the activities of mosques and any other Islamic organizations, the fertile fields for recruiting terrorists. The United States is not obliged to accept immigrants who would destroy this country or to permit them to advocate, organize or finance mass murder.

The HLF case shows that things have gone too far in this country, that Islamic terrorists are exploiting American freedom to finance domestic subversion and international terror.

The time for action is now. Let the crusade begin.