Ukraine Russia

Serhiy Nayev, Ukrainian Lieutenant General, head of Joined Forces operation observes a sea shore through a helicopter's window during patrol near Urzuf, south coast of Azov sea, eastern Ukraine, Thursday, Nov. 29, 2018. Ukraine put its military forces on high combat alert and announced martial law this week after Russian border guards fired on and seized three Ukrainian ships in the Black Sea. (AP Photo/Evgeniy Maloletka)

How Russia’s President Vladimir Putin is received today at the G-20 meeting in Argentina will be a good test of how seriously the leaders of two-thirds of the world’s population view his latest blatant and violent breach of international law.

President Trump on Thursday announced via Twitter that he will not keep his scheduled appointment with Mr. Putin in Buenos Aires. He should urge other leaders to follow his example.

On Sunday the Russian navy shot at three Ukrainian navy vessels in the Sea of Azov, wounding some Ukrainian sailors before pursuing them into the Black Sea and taking them captive. While the Sea of Azov is disputed, the seizure was in international waters, and the incident could be considered an act of war.

As Mr. Trump noted, the Russians continue to hold the Ukrainian vessels and sailors. U.S. Ambassador to the United Nations Nikki Haley called it an “outlaw act” that makes better relations with Russia “impossible.”

It is true the Ukrainian sailors knew they were testing Russia’s unrecognized claim to the Sea of Azov. The move could be viewed as provoking the Russian reaction. But Russia used excessive force in firing on the Ukrainian vessels and seizing them and their crews.

If Russia does not suffer appropriate consequences for this incident, the risk of more aggressive conflicts could escalate.

Besides shunning Mr. Putin at the G-20 meeting, what should the United States and its allies do about the latest Russian provocation?

There is already bipartisan support in Congress for more economic sanctions on the Russian government and key individuals, and widespread support for providing the Ukraine with better weapons. The U.S. Navy could also step up freedom of navigation patrols in the Black Sea.

But the real challenge will be resolving U.S.-European differences over how best to achieve European security.

On several occasions, Mr. Trump has challenged longstanding assumptions about U.S. policy in the region, for better or for worse. Mr. Putin has exploited that tension.

Issues in question range from the development of credible military deterrence against Russia’s threat to Central Europe, which would require higher European defense budgets, to Europe’s dependence on Russian energy supplies.

A good first step would be a decision by Germany to abandon the under-construction Nord Stream 2 natural gas pipeline that would bring increased volumes of Russian gas to Germany, a country that already gets more than half of its natural gas from Russia.

When German Chancellor Angela Merkel considers her nation’s options for meeting its future energy needs, she should take into account the increasing ability of the United States to supply Germany with natural gas.

She also should consider the possibility that Congress might take matters into its hands and impose sanctions not just on Russia but on German and other international firms engaged in building Nord Stream 2.

The latest Russian outrage fits the pattern of Mr. Putin’s aggression over the past dozen years. It should galvanize and re-invigorate NATO. The ball is now in Europe’s court.

And today’s G-20 meeting is a good time to show Mr. Putin that aggression is a losing strategy.