It was a sunny afternoon on Beirut’s glamorous seafront in April 1983 and the world was about to change for ever. Old men stood fishing on the rocks opposite the American embassy. Women in high heels and sunglasses strolled along the boardwalk undeterred by the civil war and the honking traffic. Just before 1pm a green Mercedes carefully drove past the embassy, scouting the entrance, and 300 yards later flashed its lights at a waiting GMC flat-bed truck. The young man driving the Texas-built truck then slowly drove up to the embassy, accelerated the wrong way through the exit ramp, hit the entrance steps, bounced up into the lobby and exploded his bomb.

It was a stunning assault using the deadliest weapon so far of the 21st century: the car bomb. It was also the first suicide car-bomb attack on a western target.

In the confined space of the US embassy lobby, the blast wave from the 2,000lb of raw PETN – an extremely powerful military explosive – was catastrophic. The explosion ripped away the front of the building: the upper floors fell like cards, killing those inside. Sixty-three people were murdered – Lebanese and Americans, many of them close colleagues of mine in the CIA. They found the hand of my boss Robert Ames a mile offshore – identified by his graduation ring.

The CIA station had been meeting on the fourth floor, in the CIA’s offices, to discuss the threat of terrorism when the bomber struck. I was lucky: I wasn’t there that day, but as a CIA agent stationed in the Middle East, I could so easily have been in the building.

For years afterwards, I kept having the same dream: sitting at the conference suite on the fourth floor, drinking coffee, chit-chatting with colleagues, waiting for the meeting to start, and then the windows bursting in, doors, ceilings, everything falling around me and the noise of the explosion. Then darkness.

What happened in that summer of 1983 in Beirut has come back to haunt us in Iraq and Afghanistan. In their decades of civil war, the Lebanese, an inventive people, refined the weapon and became the best car-bombers in the world. The bombs that go off every day in Baghdad, the very concept of the suicide driver, were developed on the streets of Beirut.

The Lebanese raided the shelves of RadioShack and turned everyday electrical items – from mobile phones and electronic garage-door openers to model-aircraft control panels – into remotely controlled detonation triggers for car bombs. The Lebanese added gas canisters to boost the blast wave – a technique used in the attempted attack in July 2007 at Glasgow airport.

The threat from car bombs now spans the globe. Anywhere and anyone, a government building, an airport, could be a target. From Downing Street to the White House, governments are turning their offices into fortresses – and waiting for the next attack.

In 1983 in Beirut, car bombs were always the number one threat. You were a fool if you drove down the same road at the same time every day, because all it took to kill you was an old car and some explosives. Instead of driving around in an armoured limousine that would have made it obvious I was an American, I used to take taxis. I bought old Mercedes taxis, and regularly changed their colour. I even picked up passengers to help maintain the disguise. And I survived because I knew just how lethal car bombs could be.

The Lebanese did not invent the car bomb; that honour goes to the Americans. The world’s first car bomb, a horse-and-car bomb, exploded on Wall Street on September 16, 1920, killing 38 people. But the Lebanese made car bombs a lot more lethal. When they planted them, it was to make the pavements run with blood. Everyone did it: the Christians, the Palestinians, Hezbollah and the Israelis.

For three decades Lebanon has been a research laboratory for car bombers. The same signature car-bomb techniques turned up in Baghdad soon after the 2003 US invasion. A lot of Lebanese car bombers just drove across the border into Syria and on to Baghdad.

We should have seen it coming. The US embassy was not the only place to be attacked. In 1982 President Reagan had sent in the US marines to sort out the aftermath of another Lebanese war: the 1982 Israeli invasion. The marines went on patrol, handed out sweets and tried to support the shaky Lebanese government.

In the background, though, the civil war was still raging. Foolishly we got involved, taking sides. The reckoning was paid in American blood.

On October 23, 1983, at 6.20am, a bomber hit the main US marine barracks with a 12,000lb suicide truck, and 241 marines were killed. There was a lot of the usual bluster about staying the course, but we were defeated – by car bombs. We fled five months later. In the right place and with the right amount of explosive, car bombs really can change history.

It’s a lesson we should have remembered before invading Iraq. In Baghdad, the car bomb swiftly became king of the highway. Car bombs, whether they are driven by suicide bombers or disguised as delivery trucks, are deadly because they disguise killing power in something so familiar that we don’t even see it – until it’s too late.

Somewhat belatedly, the US military is spending £2.1 billion a year on secret programmes run by a military task force, JIEDDO (the Joint Improvised Explosive Device Defeat Organisation), to counter the car bomb.

But even JIEDDO’s deputy director, Brigadier-General Anthony Tata, admits: “A car is a commercial entity. You go buy a car, find some old 155mm shells and you’ve got yourself a car bomb.” If you can’t pick up old artillery shells, instructions for making your own explosives are on the internet.

The car is now as basic a tool of our civilisation as a knife. It is no longer a dream of freedom; it’s a necessity. And so, with its perfect invisibility in everyday traffic, it will continue to be a decisive weapon in all future human conflict.

Robert Baer’s documentary Car Bomb is on Channel 4 tonight at 7pm

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