Russian President Vladimir Putin has long rejected widespread calls for Syrian tyrant Bashar Assad to step down — and thwarted United Nations efforts to achieve that overdue goal. Two weeks ago during the G-20 Summit in Mexico, Mr. Putin even lectured President Barack Obama on the topic, citing recent regrets the international community has supposedly experienced about forcing changes in governments in countries suffering from “internal” strife.

But the flood of refugees streaming from Syria to Turkey, along with the shots fired by Syrian forces across that increasingly tense border, long ago shattered the myth that this is merely an “internal” crisis.

That pretense was again exposed as a fraud when Syria shot down a Turkish F-4 fighter jet on June 22 — and when Turkey scrambled F-16s Tuesday for the third straight day after Syrian helicopters flew near its border.

Mr. Assad belatedly claimed this week that the shooting down of that fighter jet was “a mistake.” Some published reports cite U.S. intelligence sources who sound inclined to believe that story.

But Turkish officials, who announced that they have found the bodies of both F-4 pilots on the Mediterranean seabed, aren’t buying it. While they concede a brief border violation by their F-4, they dispute the charge that it was shot down over Syrian air space. They also insist that it was an unarmed reconnaissance plane and was attacked without warning.

Just as Syria’s version of events conflicts with Turkey’s, Mr. Putin’s continued insistence that Mr. Assad retain a role in a new Syrian government conflicts with reality.

If, as President Putin maintains, Mr. Assad can and should maintain power, why is his own military increasingly abandoning the Syrian president? More than 100 members of Syria’s armed forces — including a general — have joined those defecting ranks this week by fleeing to Turkey.

Meanwhile, the throngs of Syrians who have risked their all by first protesting, and eventually fighting, the dynastic regime will never agree to keeping Mr. Assad as part of the government.

Nor should they. Mr. Assad’s forces have committed mass murder in his failed effort to quell a widespread popular rebellion that began with last year’s Arab Spring.

According to the United Nations count, the death toll is now more than 10,000 — and some estimates are much higher.

Along the brutal way, Syrian military and security forces have frequently gunned down women and children. And on Tuesday, the Syrian army resumed its shelling of rebel positions near Damascus.

U.S. and NATO officials are understandably wary about a military intervention in Syria. Though the alliance’s air strikes helped Libyan rebels oust dictator Moammar Gadhafi last year, NATO leaders know that Syria’s armed might, including its air defenses, are far superior to Libya’s.

But Turkey is a NATO member, too — and has vowed to respond “decisively” to Syria’s repeated aggressions against it.

So no matter what Mr. Assad or Mr. Putin say, that is not an “internal” Syrian issue.

The rising risk of sustained armed conflict between Syria and Turkey further strengthens the already profound case that Mr. Assad must go.

The international community should continue to seek practical methods to advance that goal — not just for the sake of the long-suffering Syrian people, but for the sake of Mideast peace.