in Iraq and Syria, drawing the U.S. into a new war with them

Some 400,000 people have died in Syria's civil war and millions were displaced; ISIS filled

President Barack Obama made two crucial foreign policy blunders during his eight years in office that will stain his legacy - withdrawing troops from Iraq and allowing Syrian dictator Bashar al Assad's power to go unchecked, retired four-star general says.

Admiral James Stavridis, a NATO commander in Europe for Obama until 2013, said Wednesday that Obama acted too cautiously in Syria, where 400,000 people have died in the country's civil war.

'I think he'll look back in deep sorrow and some shame,' he said Wednesday on MSNBC of Obama's unenforced 'red line'.

Admiral James Stavridis, a NATO commander in Europe for Obama until 2013, said Wednesday that Obama acted too cautiously in Syria, where 400,000 people have died since 2011 in the country's civil war

Stavridis was on Hillary Clinton's list of possible running mates. He met with President-elect Donald Trump but told Morning Joe on Wednesday that he would not join the Republican's administration.

'I suppose I could, but I will not. I am content as dean of Fletcher,' he said.

A Navy admiral, Stavridis retired in 2013. Obama infamously warned Assad in 2012 that if he crossed the 'red line' and moved or used chemical weapons he would face 'enormous consequences.'

His administration prepared to go to war after Assad defied the admonishment but made an about-face after Russia intervened and brokered a deal with the Syria government to confiscate and destroy the arms.

The exiting president maintains that he was right to pull back because there is no military solution to the conflict in the war-torn country.

'The only solution is a diplomatic one, and no country in the world has expended more of an effort to pursue that diplomatic solution than the United States of America,' Obama's spokesman, Josh Earnest, said Tuesday.

Obama likely will be judged by history as much for what he did not do as for what he did, as Stavridis demonstrated today.

He first called on Assad to leave power in 2011. But the two-term president never supplied moderate rebels with enough firepower to topple him or force him to the negotiating table.

His failure to carry out threatened air strikes to enforce the 2012 'red line' over dealt a heavy blow to U.S. standing, including by some of his staunchest regional allies.

Despite providing billions of dollars in relief aid for refugees, Obama's approach has failed to quell what some have called the worst humanitarian crisis since World War Two.

Stavridis said Obama's abandoned threat to Assad 'sends a very bad' message to the world.

'The big mistake was withdrawing troops from Iraq,' Stavridis, now the dean of the Fletcher School of Law and Diplomacy at Tufts University, said. 'If we'd kept 15,000 there, you can drop a plum line to the rise of ISIS and dissolution in Syria.'

In terms of the civil war in Syria, he contended, 'It was not taking out Assad's Air Force as part of the move to get rid of the weapons of mass destruction, aka the red line.

'That was the moment where we could have made a difference with the facts on the ground. It was before Russia came in,' he said.

The Obama administration deflected Tuesday from the catastrophe in Syria, touting its victories against ISIS, which filled vacuums in Iraq and Syria, instead.

A ceasefire between the Syrian government in and militants in the city of Aleppo that came about after peace talks between Turkey and Russia collapsed on Wednesday.

Rebels and civilians were supposed to be evacuated from the city. The Turkish government says 'some forces' loyal to Assad did not honor the ceasefire and innocent Syrians remain trapped inside.

The Obama administration deflected Tuesday from the catastrophe, touting its victories against ISIS, which filled vacuums in Iraq and Syria, instead.

ISIS' territory is now 'rapidly shrinking' and the terror group has been isolated and no longer has access to foreign borders.

'We're having tremendous success against this enemy,' Brett McGurk, the president's special presidential envoy to the U.S.-led coalition said. 'But this remains an unprecedented threat. This fight is not over.'

The president met with McGurk Tuesday to discuss the multiyear effort to destroy ISIS as the United Nations Security Council gathered to debate the ceasefire in Syria between Russian-backed forces aligned with Assad and militants battling the government in Aleppo.

The diplomat rejoiced over security forces' progress in Raqqa, an ISIS stronghold that's been under siege for the last month, telling reporters after his meeting with Obama that the advance is 'proceeding quite well.'

The battle to retake Mosul, now in its second month, has been slow going.

Lt. Gen. Stephen Townsend, the top U.S. commander in Iraq, said Sunday that 2,000 ISIS fighters had been killed or wounded in the Mosul fight. Up to 5,000 fighters remain on the battlefield.

McGurk said Tuesday that U.S. coalition is putting 'relentless pressure' on ISIS there, and the military operation to retake Mosul has been the 'most complex to date.'

'In Mosul, it will take as long as it takes,' he stated.

ISIS' 'territory is now rapidly shrinking,' he said. A new map of Iraq and Syria released by the administration today shows ISIS losing 60 percent of territory in Iraq it had claimed and 28 percent in Syria.

The areas where ISIS has gained ground are in areas, primarily in Syria, that are not part of the U.S. operation, McGurk stated.

'It is significant,' he said, 'that to date that ISIL has not retaken control of any of the ground it has lost in operations we have enabled. And we're going to make sure it continues that way.'

He later stated, 'In our operations, ISIL has not retaken a speck of ground.'

The one city ISIS reclaimed - Palmyra - was part of a Russian operation.

The Russians 'claim to to be fighting' ISIS, McGurk said, but that is the only anti-ISIS mission they've underwent.

'We're not pleased about that,' he said. 'We want to wipe ISIL entirely off this map.'

The United Nations Security Council was meeting to review the ceasefire agreement in Syria as he spoke.

As many as 100,000 civilians were trapped in the city, and UN agencies are reporting indiscriminate killings. In one instance, the UN human rights division says, 82 civilians were killed on the spot by the Assad's regime.

The UN's Office for the Coordination of Humanitarian Affairs described a 'complete meltdown of humanity.'

McGurk called the deaths 'horrific,' and Obama's spokesman said 'the situation in Aleppo remains deeply troubling.'

'We're having tremendous success against this enemy,' Brett McGurk, the president's special presidential envoy to the U.S.-led coalition said Tuesday. 'But this remains an unprecedented threat. This fight is not over'

Russia's Ambassador to the UN, Vitaly Churkin, told the Security Council that militants, their families and the wounded would be evacuated Tuesday as part of a ceasefire agreement that had been acknowledged by Syrian rebels.

The fall of the last rebel-held areas in the Syrian city of Aleppo could seal the fate of the 'Obama Doctrine,' deepening the world's worst humanitarian crisis in decades and marring Obama's legacy.

With the U.S.-aligned rebels facing defeat by government forces backed by Russia and Iran, Obama's light-footprint approach to the Syrian conflict will suffer a serious blow weeks before he hands power to President-elect Donald Trump on Jan. 20.

The rebel loss will underscore the failure of U.S. efforts to stem the carnage from Syria's nearly six-year-old civil war, leading some critics to predict that Obama's record will be tarnished just as President Bill Clinton's was by his refusal to intervene to halt the 1994 Rwandan genocide.

'There is no doubt he will be hammered in historical terms,' said Aaron David Miller, a former Middle East adviser to Republican and Democratic administrations. 'The question will be why he didn't do more.'

Meanwhile, Obama's light-footprint approach to the Syrian conflict suffered a serious blow. The fall of the last rebel-held areas in the Syrian city of Aleppo could seal the fate of the 'Obama Doctrine,' deepening the world's worst humanitarian crisis in decades

While the war is expected to grind on, Assad's victory in Aleppo will provide fresh fodder for Trump, who has argued the insurgency has collapsed, and the United States should revamp its fight against Islamic State by joining up with Russia, and by extension, Assad.

Syria has been one of the main testing grounds for Obama's doctrine of relying on local proxy fighters instead of large-scale U.S. military deployments, reflecting his reluctance to be drawn back into unpopular ground conflicts like the Iraq war.

The approach has faltered in Syria, where on Tuesday the Syrian army said it could declare full control over eastern Aleppo by Wednesday.

'Leading from behind leaves a vacuum that is filled by the Bashar Assads and Vladimir Putins of the world,' said Senate Armed Services Committee Chairman John McCain, referring to how an Obama aide described his strategy. 'I think history will judge that these are unintended results that are going to cause great challenges to the United States for years to come.'

Obama has been criticized for refusing to provide sufficient arms and other support to moderate rebel groups to compel Assad and his Russian and Iranian backers to negotiate an end to his authoritarian rule.

'Obama has pursued a policy of calculated dithering in Syria, just agonizing over the choices until they no longer existed,' said Emile Hokayem, a senior fellow at the International Institute for Strategic Studies think tank.

The Democratic president has defended his policy as 'judicious.' His spokesman, Josh Earnest, said it was Obama's 'overriding responsibility' to protect the interests and safety of the American people first.

'There's no military solution to the civil war in Syria,' he said Tuesday, fending off criticisms of the president's response to the humanitarian crisis. 'What is the military proposal that would effectively prevent those deaths?'

The suggestion seems to be that the US should just occupy Syria, he said.

'I don't think there's any evidence to substantiate that claim, even if it's ones that's being made,' he said. 'The only solution is a diplomatic one.'

The administration tried to change the subject to its success against ISIS on Tuesday. 'It is significant,' McGurk said, 'that to date that ISIS has not taken control of any ground' in the areas monitored by the U.S. 'In our operations, ISIL has not retaken a speck of ground'

A Republican, Trump has vowed a dramatic shift from Obama's cautious strategy toward a more aggressive approach - although exactly how he will proceed remains unclear.

He will inherit an increasingly complicated conflict in Syria, and many analysts fear his lack of foreign policy experience could lead to dangerous miscalculations.

If Trump follows through after Aleppo's fall on his pledge to cooperate with Russia, Assad's military patron, there is a risk that frustrated moderate rebels could gravitate toward militant factions that pose a potential threat to Western interests.

As Assad himself turns from the wreckage of Aleppo to assert his authority over a fractured Syria, he will have to contend with the loss of swaths of his country for the time being and tough pockets of resistance still to crush.

The war has taken some 400,000 lives and made more than 11 million people homeless, driving many into neighboring countries or on a long perilous trek to Europe.

A Free Syrian Army fighter takes cover during clashes with Syrian Army in the Salaheddine neighbourhood of central Aleppo in August. Rebels and the Syrian government agreed to a ceasefire yesterday - a serious blow to the Obama Doctrine - but it has not held

Obama recently told an interviewer that the grim situation in Syria 'haunts me constantly' - although he insisted there was not much he would have done differently.

White House aides privately acknowledge that Syria - and other Arab countries in turmoil, such as Libya and Yemen - could leave a black mark on his legacy.

But they hope his record will be buoyed in other areas, including the landmark Iran nuclear deal, diplomatic openings to Cuba and Myanmar, the killing of al Qaeda leader Osama bin Laden and the prevention of a 9/11-style attack on U.S. soil on his watch.