AT 6:22 on Sunday morning, 26 years ago today, a huge explosion rocked my head quarters at Beirut International Airport, where the US Multinational Peacekeeping Force had been operating for more than a year. It was followed by enormous shock waves, sending equipment, papers and shards from blown-out windows flying. The office entry door had been blown off its hinges.

Outside, through a dense fog of ash, I saw the Battalion Landing Team's four-story headquarters demolished. A suicide driver had penetrated our southern peri- meter, rammed a 19-ton Mercedes truck bomb into the lobby of the building and detonated it. A similar truck bomb struck the French paratrooper HQ at Ramlet-el-Baida minutes later, killing 58 French peacekeepers.

Injured servicemen after Iranian/Syrian-sponsored truck bombing.

AP

Injured servicemen after Iranian/Syrian-sponsored truck bombing.

The death toll eventually reached 241 Marines, sailors and soldiers -- my men. It was the highest loss of life in a single day since D-Day on Iwo Jima in 1945. The coordinated, dual suicide attacks -- supported, planned, financed and organized by Iran and Syria using Shiite proxies -- achieved their goal: the withdrawal of the Multinational Force from Lebanon and a dramatic change in US policy.

The synchronized attacks had killed a total of 299 US and French peacekeepers and wounded scores more. The cost to the Iranian-Syrian supported operation was two suicide bombers dead. This was the beginning of the asymmetrical war radical Islamists waged against America and our allies. It has evolved today to be the major national-security threat to Western civilization.

Perhaps the most significant development that grew out of our Beirut mission was Iran's ascent. Since Iran doesn't share a border with Lebanon or Israel, in the early 1980s it deployed a contingent of its Islamic Revolutionary Guard Corps into Lebanon's Bekaa Valley. There, the Iranians established an operational and training base that is active to this day. Having created a state within a state, they founded, financed, trained and equipped Hezbollah to operate as a proxy army and used these Shiite surrogates to attack the US and French peacekeepers that October morning.

Iran's entry into Lebanon was a game-changer. With Syrian complicity, Iran still destabilizes Lebanon and attacks Israel indirectly, which raises its stature, popularity and influence throughout the Arab region and globally. Today Iran is capable of causing havoc on several fronts and on its own schedule, which provides convenient distractions while its nuclear centrifuges spin.

Shiite Iranian mullahs, looking to fuel instability, support al Qaeda, Hamas, Hezbollah and Palestinian Islamic Jihad, even though three of these groups are Sunni. They also back the Taliban in Afghanistan against NATO forces and use the IRGC's elite Quds Force to train, finance and equip Sunni and Shiite militias in Iraq.

Recent events offer insight into US-Iranian relations. With August's Iranian election in dispute, the Obama administration was able to engage Iranian leaders only by ignoring those who risked their lives to protest the election's illegitimacy. On cue, Mahmoud Ahmadinejad increased his challenges of Israel's right to exist, while deflecting attention from the carnage in Tehran's streets. Notably, Iran brought IRGC-trained Hezbollah thugs from Lebanon to subdue the protestors.

Meanwhile, some leaders implementing the mullahs' policies hearken back to the Beirut days. Mostafa Mohammad-Najjar, a veteran commander of the 150,000-man IRGC, was named defense minister in 2005. Najjar was commander of the IRGC contingent in the Bekaa Valley in 1983 and was directly responsible for the truck bombings. Najjar's ideological loyalty is exceeded only by the butchery he has wrought.

Gen. Ahmad Vahidi, Ahmadinejad's choice as the new defense minister, also took part in the Beirut attack and later succeeded Najjar as commander. Recognized by the mullahs for his successful service there, he was promoted in 1991 and founded the elite Quds Force.

Vahidi has an extensive background in intelligence operations and in special operations abroad. He's on Interpol's most wanted list, the Red Notices, for example, for orchestrating Hezbollah's bombing of the Jewish Community Cultural Center in Buenos Aires in 1994, in which 85 people were killed -- the worst attack on a Jewish target outside Israel since World War II. Last year, the European Union linked him to Iran's nuclear activities. Vahidi's assignment and background lays out a bloody road map of Iranian intentions.

Add to this the recent reports, confirmed by the Drug Enforcement Administration's former chief of operations, that Hezbollah operatives have formed a partnership with the Mexican drug cartels, using smuggling routes to get people and contraband into the United States.

At dawn today, Beirut veterans and families and friends of those killed in the bombings were scheduled to gather for a candlelight vigil at the Beirut Memorial in North Carolina to honor the fallen peacekeepers. Some of us with long memories are still waiting for justice to be served on Iran and Syria, while the rest of the world awaits their next affront to humanity.

Col. Timothy J. Geraghty, USMC (Ret.), is the author of "Peacekeepers at War: Beirut 1983-The Marine Commander Tells His Story."

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