President Obama has, finally, tip-toed across the Syrian 'red line' he established almost a year ago, and agreed to give more help to the rebels.
It's a Code Red decision in every sense; it will almost certainly drench Syria in even more blood and it's another danger signal that the war in Syria is escalating and spreading far across its borders.
The 'red line' the President established was the use of chemical weapons by Syrian Government forces. That, he said, would be a game changer. There is no conclusive proof that such weapons have been used, despite evidence provided by British and French Intelligence agencies.
Experts say that evidence is circumstantial, containing only minute quantities of Sarin gas. The US has provided no public proof of what it says its analysts discovered.
Nevertheless, under severe pressure from hawks in the US like Senator John McCain and criticised this week by former President Bill Clinton for dithering over Syria, President Obama has now decided that chemical weapons were used by the regime, that up to 150 people were killed as a result and that it was therefore time to 'change the game'.
Some game. The announcement came on the same day as the UN declared that at least 93,000 people have been killed in Syria up to April, probably more. A year ago it was 10,000.
That's five thousand a month. Assuming the same rate of killing since April, the figure is now over 100,000.
Into this bloodbath, the West is about to send planeloads of weapons. Syria's rebels, a loose alliance of army deserters, Sunni civilians and Al Qaeda-linked Islamist fanatics are now to be armed to the teeth by the world's only superpower.
Oh, of course the wise policy makers of Washington make reassuring noises about the clear distinction they see between these rebel groups; they'll help the 'good' ones, while keeping weapons away from the Friends of Al Qaeda. Well, let's see. Because their wisdom is about to be tested.
The announcement from the White House was almost deliberately vague. America will provide more help for the rebels, beyond the non-lethal aid it gives at the moment, but no-one spelt out the details.
There has been bitter division in Washington for months about whether and how to help rebels. Unnamed 'officials' were quoted, saying America would send small arms, ammunition and anti-tank weapons. But a decision appears to have been taken, for now, not to send heat seeking anti-aircraft missiles, which the rebels say they need to destroy the Government force's air superiority.
Officials have stressed how careful they will be to vet which groups get weapons. The leader of the main rebel group, the Free Syria Army, General Salim Idris, believes his men will have new weapons within weeks.
But they, of course, are not the most effective rebel group. That honour belongs to the Al-Qaeda linked Jabat al-Nusra. Somehow the weapons will never find their way into their hands.
It is, say the Americans, an attempt to level up the battlefield; to allow the rebels a fighting chance against the jets, tanks and superior forces of President Assad. It's also a way of trying to ensure that if Assad falls and the battle for control of Syria pits Western linked rebels against Islamists, then the 'good' rebels have a better chance of winning.
So it's a bet on the long term future as well as the short term battles to come.
But it's a gamble of huge proportions, endangering still further America's moral and military capital.
The West is now directly involving itself in killing. America says there will be no troops on the ground, although it's clear CIA and Special forces trainers will be used to deliver whatever weapons are sent.
It has been considering the establishment of 'No Fly zones' and 'safe areas' inside Syria's borders but says no decision on these has been taken. But make no mistake, if you hand a man a gun and he kills with it, you are an accomplice to murder. Britain, which has been egging on the Americans, is in the same moral boat, just ten years after both countries went to war with Iraq over weapons of mass destruction both governments assured us were there.
It's a gamble for another reason. It's one thing for a few thousand fighters from Hezbollah to join the war, or for the Gulf state of Qatar to supply weapons, it's quite another for the world's strongest power to back Sunni rebels against Shia forces in a Middle Eastern civil war. America has a poor record in the Middle East. It may be about to get worse.
And the war threatens to get worse too.
Already the danger is not just deadlier fighting within Syria. That's already happening. Government forces are beginning a new offensive against rebels who control half of Syria's second city, Aleppo. Fresh from victory in the strategic town of Qusair, Syria's army is turning to the nearby city of Homs, the cockpit of the revolution. America may believe that by arming the rebels it can halt the regime advance before both cities are re-taken.
But the war now involves fighters from the Lebanese group Hezbollah. They provided the muscle that made Qusair fall.
Hezbollah, and Syria's army, are being supplied by Iran. Russia is supplying President Assad's forces with light and heavy weapons. America is about to supply their enemies. It's the Cold War all over again. This time fought in the most volatile region of the world. It's a proxy war that pushes American-Russian relations to a new low. The possibilities of miscalculation are endless.
America is now entering a sectarian war, that is already spreading beyond Syria's boundaries. On the one side is a Sunni Muslim front, led by Saudi Arabia, backing the rebels. On the other is a Shia front, led by the Saudis' sworn enemy Iran. America is now entering this intra-Muslim war, while at the same time confronting Iran. Its weapons against the Ayatollah's.
It's a war President Obama fought for two years to avoid. He opposed the war in Iraq and made it his business as President to get out of both Iraq and Afghanistan. Half way through his Presidency he now finds himself tip-toeing into the Syrian minefield.
It's a war that is spreading. Syrian rockets and missiles have already landed in three neighbouring countries, Israel, Lebanon and Turkey. Syrian troops have been killed fleeing into Iraq. Turkish warplanes have struck inside Syria; Syrian car bombs have killed dozens inside Turkey. Iraq's civil war has been re-ignited by the sectarian slaughter in Syria, with over a thousand killed in the worst month of violence for five years.
The biggest danger is that the war in Syria will explode inside Lebanon. It's a fragile country, with terrible memories of a civil war that tore it to pieces. It is dominated by the group now fighting inside Syria, Hezbollah. And there has already been some fighting in Lebanon itself, between Sunni and Shia factions who support different sides in Syria. Lebanon is a tinderbox waiting to explode.
Syria, President Assad once declared, is different. What he meant was that it would be safe from the Arab revolutions. In that he was wrong. But he was right in saying that while Libya imploded, Syria would explode across the Middle East if violence grew. Syria's revolution has done what revolutions often do, it has 'changed utterly'.
So, in the next few days many of the world's most powerful leaders will gather to discuss Syria. It will be one of the frostiest Summits ever and perhaps one of the least successful ones. At the G8 meeting in Enniskillen, President Obama and Russia's President Putin will glare at each other, as rivals across a Middle Eastern chessboard. Both have agreed peace talks are necessary and both signed up to a conference in Geneva this month. That has been postponed indefinitely. Instead, both are backing their own sides in a sectarian slaughter in Syria. David Cameron will host a chilly preview to the summit when he meets Vladimir Putin in Downing Street.
The summit is unlikely to achieve much, certainly not peace in Syria. Never believe a war cannot get worse. In another year, 93,000 dead may seem like 10,000 did a year ago.
This article first appeared in Saturday's Daily Mirror.