The president of the European Central Bank has started to deliver on his recent promise to do whatever it takes to save the euro.
It is the most ambitious action yet to stem Europe's sovereign debt crisis.
Listen to my analysis from this morning's edition of AM.
Throughout this crisis the can certainly has been kicked down the road, but importantly today we are seeing unprecedented bond buying, which will give the eurozone more breathing space to get out of this crisis which has been running now for three years.
The ECB's action is intended to ensure that Spanish and Italian bond yields will no longer be able to rise to the post-euro highs we have seen over recent months that had threatened to make both nations' debt repayments unsustainable.
The key words in the ECB announcement are "unlimited bond buying", which could mean hundreds of billions of euros from the ECB.
However, there are conditions: countries like Spain and Italy must first request help from the Europe's bailout fund, and commit to economic reforms and austerity, before the ECB will actually step in to buy their bonds.
Under the program, called Outright Monetary Transactions, the ECB will step in to buy an unlimited quantity of bonds that financial markets do not like or want.
That could be enough to help these countries turn themselves around, but the ECB rescue may be very costly, maybe putting more than 1 trillion euros on the line in bond purchases.
There are risks that the ECB simply gets stuck with a lot more debt on its books for little long-term benefit, with Spain and Italy taking the chance to rack up more debt at lower interest rates.
However, when pressed on this point, the ECB president Mario Draghi made it clear that the central bank would pull the plug if indebted countries do not play by the rules.
"We want this to be perceived as a fully effective backstop that removes tail risks from the euro area. We want this," he told reporters at a press briefing after the meeting.
"But, at the same time, if we reach our objectives why should we continue doing so? If governments or countries do not comply, why should we continue doing so?"
The decision by the ECB was not unanimous.
There was one significant dissenting view from Germany, with its central bank governor voting against this bond buying measure.
That was anticipated, though, given Germany's recent protests that the ECB was breaching its mandate and possibly EU law, and also risking an outbreak of inflation.
The German industrialist and former head of IBM Europe Hans Olaf Henkel is one very vocal critic who says the ECB's strategy is flawed.
"The European Central Bank has totally gotten under the control of politicians. They will save the euro to the death," he said.
"As far as the conditions are concerned, with the exception of Ireland, all those countries have meanwhile dropped all commitments which they made. The politicians are making a mistake."
However, the move got almost unanimous support from investors, with European markets surging on the news.
Spain's main share index rocketed almost 5 per cent, even though under this strategy it would need to seek a fully blown bailout in the first instance from the EU to qualify for the bond buying program.
So, in some ways, investors are getting excited about something that could actually be quite bad news.
In the US, the Dow Jones Industrial Average closed almost 2 per cent higher, with both it and the broader S&P 500 jumping to their highest levels in more than four years.
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