Tuesday's attack on the United Nations headquarters in Baghdad was devastating confirmation that the world body's blue and white olive branch motif - which flutters on flags and decorates tailfins - does not necessarily afford protection.
But while this may have been one of the worst attacks since the UN was established in 1945, it is not the first time it has been targeted by those who do not welcome its intervention or agree with its attempts to secure peace.
Dozens of civilians died in a strike on the UN's Qana compound
High-profile servants of the body have been assassinated or killed in mysterious circumstances, while more than 1,500 international peacekeepers have lost their lives since the first such mission was deployed in 1960.
UN compounds may visibly fly the sky-blue flag but it has not shielded them from angry, stone-throwing locals or organised militia furious at what they see as meddling in their sovereign affairs.
The UN's involvement in the Arab-Israeli dispute has proved problematic from the outset - accused by Palestinian sympathisers of failing to enforce resolutions against Israel, while at the same time regarded by Israel as a hostile entity.
One of the most infamous killings in the organisation's history - the assassination of UN mediator Count Folke Bernadotte - occurred during the body's first peace mission in 1948, just after the state of Israel was declared and war broke out with the Arab states.
Count Bernadotte, who in the course of trying to negotiate ceasefires had suggested establishing Jerusalem as an international city, was killed by Israeli extremists in September of that year.
1948: Count Folke Bernadotte assassinated
1961: Secretary General Dag Hammarskjold and 15 others die in plane crash
1996: 100 civilians killed at UN compound in Lebanon
1998: 14 die in Angola plane attack
1945-2002: 1,580 peacekeepers killed
Relations between Israel and the UN have remained fraught down the decades.
In the worst attack ever on a UN site, more than 100 Lebanese civilians who were sheltering in a compound of the body's observer force in southern Lebanon, near the village of Qana were killed in a strike by Israeli artillery in 1996.
The Israelis said it was a tragic mistake, but a UN inquiry by a Dutch general concluded that the shelling was probably deliberate.
Just over a decade after the assassination of Count Bernadotte, the UN was again to lose a high-profile figure - this time its secretary general, the Swede Dag Hammarskjold - in 1961.
Mr Hammarskjold met a premature death in a plane crash that has never been entirely explained as he was trying to mediate a peace agreement between the newly-liberated former Belgian Congo and Moise Tshombe, leader of the breakaway diamond-rich province of Katanga, and bring an end to the civil war.
East and West were at loggerheads over the region, its riches, and its political sway. There are various theories as to why both sides in the Cold War could have wished the Swede dead.
Fifteen others died in the plane crash.
The Congolese civil war also saw the UN's first major deployment of peacekeepers. Some 19,000 troops were sent, 250 were killed.
After the trauma of that operation, the UN kept its head down for the next 20 years.
All peacekeeping activities from the mid-1960s to the mid-1980s were confined to small-scale and consensual operations.
Africa was again, however, to be the scene for some serious UN losses in the 1990s, when the body decided to get involved in the Angolan civil war.
On 26 December, 1998, militants shot down a UN aircraft which had been delivering logistical equipment to UN forces in the central highlands. Fourteen people were on board the downed plane, including 10 UN staff and four crew members.
One week later on 2 January, 1999, a second UN aircraft was shot down, also by Unita rebels.
The C-130 transport plane, which was flying from Huambo to Luanda, had four UN personnel and four crew members on board.
The UN observer mission had been repeatedly condemned by the Angolan Government for what it saw as its failure to stop the Unita rebel leader Jonas Savimbi, from stockpiling weapons.
The UN Secretary General, Kofi Annan, also conceded that the international community could have done more.
And it is not just governments who sometimes want more from the body than it is willing or able to give, or feel that it shows bias in its dealings.
The organisation's behaviour in Kosovo, a UN protectorate within Serbia and Montenegro, has been a source of frequent controversy.
The town of Strpce, 25 miles south of Pristina, has been the scene of a string of confrontations between villagers and UN police over the past four years.
In 2000, hundreds of Serbs attacked a UN office, breaking windows, burning computers and setting UN flags on fire.
Since Serbian troops left Kosovo in 1999 and peacekeepers moved in, the remaining Serbs have often accused the UN of favouring the majority Kosovo Albanians and not doing enough to protect them.
But it was not until this month that the UN lost its first member of staff in the province since it came under UN control.
Satish Menon, a UN policeman from India's southern state of Kerala, was shot dead while travelling in a police car near the village of Slatina.
He was travelling in a car that clearly bore the UN's logo.