I've pointed out that Turkey and the U.S. are in an armed standoff over the city of Manbij, Syria.
Largely overlooked is a dangerous escalation of tensions between two NATO allies.

Last week, a low-flying Turkish helicopter had passed provocatively close to a military base on the nearby Greek island of Ro, drawing warning shots from soldiers. That incident was followed three days later by the death of a Greek fighter pilot who crashed, his government said, after attempting to intercept a Turkish aircraft that had entered the country’s airspace.

In all, the number of incursions by Turkish military ships and jets into Greek territory has spiked in recent months, according to Greek officials, stoking concerns of a new military conflict in a region where Turkey is already embroiled in the war raging in Syria.

This probably won't turn into war. After all, Greece and Turkey have been disputing over ownership of small islands since the Turks were called Ottomans, and very rarely did it end in shooting.
Nevertheless, there is something different this time.

The neighboring countries have been at war with each other several times in the 20th century and were close to military conflict over the Greek islet Imia in 1996, before the United States stepped in to avert disaster.

The NATO allies are now at the brink again, goaded by populists on both sides — and this time, Washington is nowhere to be found.

On Monday, a Greek-Turkish confrontation rekindled old memories. Turkish Prime Minister Binali Yildirim, during an event in Ankara, claimed that the Turkish coast guard had removed a Greek flag from an islet near the island of Fournoi, after it was placed there earlier by three Greeks.

Besides the lack of a coherent foreign policy from the White House, the standoff at Manbij reduces Washington's leverage with Turkey.
Another thing that is different is the sharpness of the words out of Ankara.

Turkey’s position was reiterated by Erdogan during his visit to Athens last year. He claimed that the Treaty of Lausanne needs to be reconsidered, evoking the Turkish-speaking minority of Thrace, a region of northern Greece, as justification. As if to underscore Erdogan’s intentions, Turkish warships recently stopped an Italian research boat from reaching its destination in Greek Cypriot waters.
Even amid this dangerous climate, both sides are indulging in reckless rhetoric...Kammenos, as defense minister, has repeatedly taunted the Turks, making statements along the lines of “let them come and get it.” Kammenos’s deputy in the Ministry of National Defense, the leftist Fotis Kouvelis, said on Monday night that Greece finds itself in “undeclared war in the Aegean.”

Greece is being careless with their rhetoric, but Turkey is being outright belligerent.

“Erdogan is a little bit out of control — he’s picking a lot of fights and there is a lot of uncertainty about how far he’s prepared to go,” said Nikos Tsafos, who researches the politics of the Eastern Mediterranean at the Center for Strategic and International Studies, a Washington-based think tank.
“The odds of something going wrong are increasing on a weekly basis,” he said.

Now we are seeing the costs of having a man-child in charge, and no check on the Pentagon.