The murderous terrorists who destroyed the World Trade Center towers in Manhattan and damaged the Pentagon, delivered a very clear and sobering message yesterday: The leader of the free world is vulnerable.

Blame and responsibility for the most devastating terrorist attack in American history must be laid squarely at the feet of those who masterminded and perpetrated yesterday’s mayhem. The security of the free world demands that they are identified and punished.

And yet terrorism does not happen in a political vacuum. The policies pursued by Western nations impact directly on both the means available to terrorists and the motivations driving their evil agendas. It is imperative that we assess what has gone wrong and begin to set those policies right.

Despite its stated policy of not negotiating with terrorists, the years of the Clinton Administration saw the United States going out of its way to appease some of the 20th Century’s most notorious terror groups.In the name of peace, the U.S. has pursued a risky policy of conferring the imprimatur of legitimacy on the affiliates of terrorist movements. For a time this appeared to pay off. Peace talks were all the rage; cease-fires seemed to follow one another and left the impression of progress. When terrorists warned of attacks against U.S. or Western targets, the Clinton Administration chose to see these threats as internal propaganda only.

The peace talks seemed to move the terrorists to ever bolder acts of violence. In Israel, the “land-for-peace” initiative sounded good, but in practical terms, it meant subsidizing a multitude of radical Palestinian groups, ranging from Arafat’s Fatah branch of the PLO and its military wing, the Tanzim, to the socialist-nationalist Popular Front for the Liberation of Palestine, headed by George Habash.

This erroneous policy legitimized the PLO by giving it control of the West Bank and Gaza — which came to be known under the Oslo agreement the Palestinian Authority. The failure of these accords is well known.

Also bear in mind, the Clinton Administration’s legitimization of Gerry Adams and the IRA. The IRA — for which Mr. Adams’s Sinn Fein is a political front — has not abandoned its violent tactics and criminal activities. The terrorist group’s refusal to hand over weapons currently risks undoing the “peace process” in Northern Ireland, an area that a British minister said last week was once again descending into chaos.

The “peace initiatives” for the IRA and the PLO have failed for a very simple reasons: Both groups pursue objectives that are incompatible with free-market democratic society. To the extent that “peace” means democratic representation — and thus a loss of the political control that keeps them in business — these groups fear it and are determined to see these processes derailed.

To understand the visceral aversion to the values that Western democracies hold dear it helps to recall the roots of these terrorist organizations. The PLO and the IRA became Marxist-Leninist organizations in the 1960s; the PLO almost from its inception, and the IRA in 1969. The Soviet Union and its European and Latin American satellites initially sponsored both. Their training included unconventional warfare, ranging from terrorism to other criminal activities, especially drug trafficking — an amalgam that both adopted early on.

The economic incentive was clear: drug money provided the resources to carry out their revolution. Though the motives of the two groups were different, their goal was the same: to destabilize and undermine legitimate, democratic governments.

Long after these Marxist rebels have replaced their social agenda, they continue their wide-ranging international criminal activities under the cloak of fighting an idealistic campaign for a subject people or against the oppression of the powers that be. No longer motivated by ideology, but rather by greed, these organizations have built criminal empires that have all but obscured their respective societies. When ostensibly negotiating at the “peace” table, they have and are filling their pockets with ill-gotten gains, while manipulating the media into portraying themselves as victims seeking justice.

And the world has fallen into this propaganda snare despite numerous congressional records and other national and international law enforcement reports documenting the extent of their criminality.

The PLO was in the drug trafficking business almost from the start. Operating from Lebanon, under George Habash’s leadership, and assisted by a PLO-owned shipping company, the organization exported hashish, opium, heroin, and cocaine, first to Europe and later to the U.S. and Australia. In return, they obtained weapons for their war against Israel and the West and amassed a massive treasure trove.

Britain’s National Criminal Intelligence Service estimated the PLO’s ill-gotten gains to total between $8 billion to $10 billion. The organization also enjoys an annual income of about $1.5 billion to $2 billion from “donations, extortion, payoffs, illegal arms dealing, drug trafficking, money laundering, fraud, etc.”

Since then, Washington has unwittingly aided and abetted the PLO’s criminality. Since the start of the Oslo process, Mr. Arafat has received at least $3 billion more from the United States and the international community, without any serious demand for accountability. Mr. Arafat, in sustained and well-documented instances of corruption, has been systematically skimming off portions of these funds, as he has with monies given to him on behalf of the refugees in the camps.

True to form, the political leadership of the newly created Palestinian Authority (overwhelmingly culled from the ranks of the terrorist PLO) has continued to plunder funds intended to assist the populations of the West Bank and Gaza. The personal wealth of Mr. Arafat and his inner circle has not gone unnoticed by the Palestinian masses since most live in dismal conditions. The Intifadah was incited by Mr. Arafat and his circle a year ago as demonstrations in the West Bank and Gaza against this corruption began to threaten Mr. Arafat’s leadership.

It is difficult to judge the scope of either the IRA or the PLO’s criminal empires; both are estimated to be in the hundreds of millions of dollars and have wide global reach.

This information is not new. Rather, it can be found in numerous U.S. Congressional hearings and many international reports on the worldwide dangers of organized crime, terrorism, and corruption. The horrible attacks yesterday sent a cruel but realistic wake-up call. Take terrorists at their words, and remember that these criminal organizations work together. It is time for the Bush Administration to treat all terrorist groups and their representatives as a threat to international security.