Some officials called it the UN’s own version of 9/11. The similarity deepened at the end of October, when an internal report came to the withering conclusion that the UN had put its own staff in harm’s way by failing "to comply with its own security regulations."

The report – which came amid a sharp escalation of terrorist attacks, including a suicide bombing that destroyed the Baghdad headquarters of the International Committee of the Red Cross – helped precipitate the withdrawal of virtually all remaining UN and non-governmental humanitarian aid workers at the end of October.

Of course, it was not as if the UN and its bedrock impartiality had never come under attack.

Over 1,800 peacekeeping personnel have lost their lives since 1948 – the same year that the UN’s Mediator for Palestine, Count Folke Bernadotte of Sweden, was assassinated in Jerusalem. In the last decade, nearly 200 civilians working as UN humanitarian aid workers were targeted and killed. In 1964, anti-Castro Cubans fired a bazooka shell at UN Headquarters from the Queens side of the East River, but it fell harmlessly into the water. And just last year, a Korean-American who said he was protesting North Korean policies drew a handgun and calmly fired seven heavy-caliber bullets into the Secretariat building, narrowly missing several UN workers.

The attack in Baghdad was of a wholly different order. Never had the UN been assaulted with so devastating a weapon – an explosives-packed garbage truck parked directly under the office window of the Mission Chief, Sergio Vieira de Mello. The huge blast, detonated by the unidentified suicide driver, left some 150 people wounded along with the 22 fatalities. Most of the victims died in a lethal hail of splintered window glass.

For the UN and its staff, the shock and grief are still fresh.

"This is a time of almost unbearable sadness," Secretary-General Kofi Annan acknowledged. "Our United Nations family has been the victim of an attack so brutal and barbaric that we are still struggling to take it in."

For many, the attack seemed a logical outgrowth of what they saw as the Organization’s hapless efforts to head off a war that was arguably an egregious violation of the UN Charter – a premeditated act of aggression against a Member State that had not attacked first.

The shock was especially lingering in New York. A number of victims had only just arrived in Baghdad from jobs at UN Headquarters, and many were career officials who were well known throughout the UN System. Months later, survivors’ stories were still being exchanged in the corridors, where colleagues stop to chat and in memoriam editions of in-house publications like Secretariat News and UNICEF Staff News were still in ample supply.

"I instantly knew it was a bomb," recalled Kim Bolduc of the UN Development Programme, who was sitting at a conference table with five colleagues when the windows blew in. "I thought I was dying."

"Then the lights came back on, too bright; the generator was working, the dust and debris were settling down, and I saw everybody sitting at the table, bleeding, perfectly still and silent.

"There was so much blood," she wrote in UNICEF Staff News, "that for a few seconds I didn’t know if this was a nightmare or a vision after death."

One of her colleagues at the conference table, Christopher Klein-Beekman, died instantly in his chair. Klein-Beekman, a humanitarian aid worker of immense talent, had been serving as UNICEF’s acting director of Iraq programs. He was 31 years old.

The death of the ranking UN official, 55-year-old Sergio Vieira de Mello, cut especially deep because of his personal charm and his extraordinary gifts for international diplomacy, which were so dazzling that he was often mentioned as a future shoo-in for UN Secretary-General.

"Very early on he was marked as a man of exceptional ability in an organization full of high achievers," wrote Shashi Tharoor, who met de Mello when they both worked for the UN High Commissioner for Refugees (which de Mello joined when he was 21).

"He had all the skills of the international diplomat," said Tharoor, now Under-Secretary-General for Communications and Public Information. "Grace and elegance, self-confidence in unfamiliar situations, a talent for communicating easily across cultural barriers, an instinctive respect for other points of view – and a remarkable fluency in several languages."

Little surprise that de Mello – universally known affectionately as Sergio – charmed not only Iraq hawks Condolezza Rice, Paul Wolfowitz and the American pro-consul Paul Bremer, but George W. Bush himself.

Sergio’s earlier success in restoring tranquility to Kosovo and, in short order, East Timor, made him Kofi Annan’s obvious choice to take on the daunting challenge of Iraq, where the US seemed determined to minimize the UN’s role. He took the job, but made no secret of his reluctance. What he most wanted was to take up his pre-war appointment as UN High Commissioner for Human Rights.

My most direct personal connection to the August 19 catastrophe was through Salim Lone, a longtime friend and colleague - and the only known Silurian who was caught up in the Baghdad attack.

Salim had been a journalist in Kenya whose outspoken women’s magazine, Viva, so infuriated the Arap Moi Government that he fled for his life in 1982. He arrived in New York almost penniless, but eventually found work at the UN Department of Public Information.

After more than two decades of distinguished service, Salim – a 60-year-old with 20-something energy – was facing mandatory retirement in July when he got an unexpected retirement gift: a three-month appointment as Sergio’s Director of Communications. It seemed like the perfect cadenza to Salim’s career, and at his joyous send-off party, I remember laughingly advising him to "Keep your head down."

It never occurred to me that the suggestion might be useful. At the time, few of us thought that postwar Iraq was a dangerous environment, especially for so seasoned a group of UN veterans. As it happened, Salim somehow kept his head low enough to avoid serious injury, but the details were a mystery. "I just do not know how I escaped the huge shards of glass that flew into the room from the window behind me," he told UN Chronicle magazine.

Before his near-death experience, Salim said, he had planned to spend his retirement working to make "a small contribution to improving relations between Islam and the West.

"But now, after this terrible atrocity against the United Nations," he told The Chronicle, "I feel doubly or triply or quadruply committed to doing something in that area. But how I’ll do it I’m not yet sure."