Two years ago Mario Draghi declared he would do “whatever it takes” to save the eurozone from the threat of a breakup amid mounting market pressures on the euro.

Now the European Central Bank chief has unveiled a sweeping package of measures to head off a new threat to the 18-member currency bloc - deflation choking off the region’s recovery from a protracted recession.

This included Draghi taking the ECB into unchartered waters by announcing yesterday that the bank was lowering its key deposit rate to below zero and cutting its benchmark refinancing rate to an historic low of 0.15%. The refinancing rate has stood at 0.25% since November.

Significantly, this was first time that any major central bank has decided to drop a key rate into negative territory.

Underscoring the scale of the measures to haul the eurozone out of low inflation spiral, financial markets had already dubbed yesterday as “D-Day” for the euro.

“Taken everything together, today’s package underlines the ECB’s determination and willingness to act,” said ING Bank economist Carsten Brzeski.

But bold action to shore up the currency bloc has been a hallmark of Draghi’s two and half years at the helm of the Frankfurt-based ECB.

Shortly after taking over from Jean-Claude Trichet in November 2011 as the euro’s chief custodian, Draghi launched a series of rapid-fire cuts in borrowing costs as part of efforts to shore up the eurozone’s struggling economy.

He followed this up at the end of 2011 by announcing a new long-term cheap loan programme totalling more than 1tn euros ($1.36tn) to pressure banks to lend to the eurozone’s embattled small-to-medium sized business sector.

Under Draghi’s leadership, the ECB has also taken steps to open up the bank’s decision-making process including taking the unprecedented step of introducing a policy of forward guidance on its plans for interest rates.

A short time later, the ECB president saw off tough opposition from Germany to push through a controversial plan to buy government bonds if necessary to help the eurozone’s cash-strapped member states.

In addition to the cuts in interest rates, yesterday’s package of measures unveiled by Draghi includes some which the ECB hopes will boost liquidity in the eurozone.

It also could eventually pave the way for the ECB to introduce a US-style quantitative easing programme of monetary stimulus to boost inflationary pressures and keep the eurozone economy on a growth track.

Apart from hitting wages and driving up the cost of debt, low inflation could lead to consumers delaying purchases in anticipation of further declines in prices, which would in turn undercut household spending and economic growth.

The round of moves announced yesterday comes after months of threats by Draghi and senior ECB members to act to spur economic activity and bank lending.

But since the bank’s 24-head governing council met four weeks ago, further signs have emerged of the fragile state of the eurozone economy.