Donald Trump was right about Syria and red lines. Barack Obama made a big mistake in 2012 and 2013, when he declared the use of chemical weapons a line that could not be crossed, and then did nothing.
The critics who complain that the U.S. President shouldn't have responded to a chemical-weapons attack that killed more than 70 people by pointing the finger at his predecessor are right, of course. It won't do anything to stop Syrian President Bashar al-Assad gassing people again.
But Mr. Trump was right that it was a debacle. Mr. Obama's actions – setting "red lines," threatening air strikes, and then balking – made Mr. al-Assad believe he could repeat his chemical weapons outrage.
It's worth remembering that now – and not to inflate a new President whose foreign policy has been incoherent. Mr. Trump has just said the chemical weapons attack in Khan Sheikhoun crossed "many, many lines," and reports say he is considering military options.
That's what was happening four years ago, when Mr. Obama prepared a bombing campaign to punish the Assad regime for crossing a red line – using chemical weapons.
That was a rare war crime. In a century of horrors after the First World War, when the use of chemical weapons was outlawed by international convention, they were used in only a handful of conflicts, most notably by Saddam Hussein in the Iran-Iraq war. Even in the grim catalogue of atrocities in Syria's civil war, Mr. al-Assad's use of chemical weapons stood out.
Mr. Obama himself underlined it. In 2012, he declared that the use of chemical weapons was a red line that must not be crossed. In 2013, after evidence emerged that Mr. al-Assad's forces had used chemical weapons, Mr. Obama prepared to bomb.
Then things fell apart. British prime minister David Cameron, a key ally for strikes, fumbled the politics and lost a vote in the Commons. Then Mr. Obama, who had lined up international support – Australia's Kevin Rudd backed him in the midst of an election campaign, and Canada's Stephen Harper offered support – suddenly announced he would consult Congress. The strikes were off.
Of course, Britons and Americans were war-weary. And strikes wouldn't have been a simple matter. There can be civilian casualties and unpredictable consequences. Western governments had to consider whether they'd be forced to secure chemical-weapons stockpiles before Islamist extremists captured them.
But Mr. Obama drove the threat right up to the edge, then suddenly backed off. U.S. leadership was weakened. The threat of consequences for using chemical weapons was hollow.
Canada's then-foreign affairs minister John Baird said he was "stunned." Mr. Obama didn't need to invade Damascus, he said. "Twenty-five cruise missiles taking out 25 military facilities would have sent a clear message not to do it again," he said this week.
"Now that Assad has proven he can get away with it, even after all that happened, he's using them again," Mr. Baird said this week. He said he believed, based on "serious allegations," that the Assad regime used chemical weapons six or seven times since the red lines, on a limited scale. The difference with Khan Sheikhoun is that there is video, he said: "This is the legacy of the former president's retreat."
There's not too much controversy in the idea that backing away from red lines was a self-inflicted blow for the U.S; John Kerry, Mr. Obama's secretary of state, said it was a mistake that weakened the U.S. in the Middle East.
Now, intervening is even more complicated. The Assad regime, murderous as it is, is today generally viewed as less of a threat to the region than the Islamic State. The Russian military is in Syria supporting Mr. al-Assad.
And the lesson Mr. Trump should learn from Mr. Obama's error is to act in a non-Trump way. It's a mistake to reach for sweeping rhetoric, or start calling for regime change. Set out the case deliberately. Think of punishment to deter the use of chemical weapons, with the threat of more if it's repeated. And for the President, whose base includes isolationists who believe America First means avoiding foreign entanglements, the lesson is not to threaten big unless you're going to act.