The sudden announcement that Libya is giving up its ambitions to develop weapons of mass destruction is a major step in the effort led by the United States to stop their spread around the world.
The move by Colonel Muammar Gaddafi and the capture of Saddam Hussein are two very welcome seasonal presents for President Bush and Prime Minister Blair.
Libya is trying to repair international relations
It will help to soften their disappointment that no such weapons have been found in Iraq.
And it shows that countries can be persuaded not to go down the path of developing weapons of mass destruction.
The message to North Korea, Iran and Syria in particular is clear. If you co-operate, you will benefit. If you do not, there will be trouble.
1992/1993 UN imposes an air, arms and oil equipment ban on Libya to get Tripoli to hand over Lockerbie suspects
1999 Sanctions suspended when Libya turns them over
September 2003 Sanctions lifted after compensation agreed over Lockerbie and with France over 1989 bombing of a French airliner
Dr Gary Samore of the International Institute for Strategic Studies (IISS) in London said: "We want to get the word out that if countries give up their programmes, there will be rewards."
Colonel Gaddafi appears to have got the message of Iraq - that developing such weapons or even showing an interest in them is highly dangerous.
It was perhaps no coincidence that he approached Britain and the United States in March, the very moment that Saddam Hussein was being driven from power.
1981 President Ronald Reagan bans use of US passports for travel to Libya
1982 Imports of Libyan oil and some exports banned
1986 After the Berlin disco bombing, sanctions are widened to include direct import and export trade
1996 Iran-Libya Sanctions Act is passed.
2001 Act amended to allow punishment of non-US firms investing in Iran and Libya's energy sectors
2003 Washington says it will maintain US sanctions after UN sanctions lifted
Libya has another motive, though, in making this decision.
It's the culmination of its policy of re-engaging with the outside world. The mercurial Colonel Gaddafi, who has been in power since 1969, realized that a new wind was blowing and he wanted to come in from the cold.
First he had to settle the issues arising from the Lockerbie bombing, which he did earlier this year with an admission of Libyan responsibility and a $2 billion compensation payment.
That got UN sanctions lifted.
But he needed bilateral American sanctions removed as well because these hold up development of his oil. Libya remains a major oil producer. It is seventh in the Opec oil cartel's top 10. But it needs to modernise.
The Colonel knew he had to do more and he has now promised to do so in a typically dramatic fashion.
There is still some way to go. The United States has yet to lift its own sanctions.
These are a ban on trade - including oil - and penalties for non-US companies which invest more than $20m a year in Libya's oil industry.
And Washington still classifies Libya as a state sponsor of terrorism.
However, President Bush hinted that the United States might soon move, presumably if Libya keeps its word.
"Leaders who abandon the pursuit of chemical, biological and nuclear weapons and the means to deliver them will find an open path to better relations with the United States and other free nations," he said
It has often been alleged that Libya was trying to develop chemical weapons, though the extent of this programme was unclear.
Dr Gary Samore of the IISS said: "Libya is believed to have had a chemical weapons programme for 20 years."
In 1987, its neighbour Chad accused it of using mustard gas in a conflict there.
The big surprise, though is its reported development of nuclear technology, though exactly how far this got remains to be clarified by international inspectors.
Over the years, Colonel Gaddafi has hinted that Libya and other Arab states should go nuclear because Israel has.
The Federation of American Scientists, however, made this assessment: "In recent years, concerns about Libyan nuclear ambitions have faded, though apprehensions about Libyan chemical weapons efforts remain very much alive.
" Libya is no position to obtain access to nuclear weapons in the foreseeable future, given the extremely limited domestic technical base of the country. "
Until now, it was assumed that Libya's membership of the Nuclear Non Proliferation Treaty meant that inspections by the International Atomic Energy Agency were effective.
If they have not been, that is very worrying.
Another important aspect of the agreement with Libya is its undertaking not to develop missiles with a range beyond 300 kilometres.
Dr Samore said that this limit has been set by the group of supplier countries known as the Missile Technology Control Regime.
The MTCR reckons that a missile with a shorter range (and payload of less than 500 kilograms) is unlikely to deliver nuclear weapons, so can be regarded as a tactical weapon.
It is an amazing turnaround for Colonel Gaddafi, whose own compound was bombed on the orders of Ronald Reagan in 1986.
He has also supplied the IRA with weapons.
Now he is being lauded by both the US and the UK.