President Donald Trump (L) and Russian President Vladimir Putin arrive for a joint press conference after their summit on July 16, 2018 in Helsinki, Finland. (Photo by Mikhail Svetlov/Getty Images)

MUNICH – There are few better places in the world than here to reflect on the need to end Western appeasement of Vladimir Putin and his growing list of international crimes. The latest was last Sunday's Russian attack on Ukrainian naval vessels in the Black Sea – and its purpose of asserting Kremlin control over its still-sovereign neighbor.

This Bavarian city of beer halls and baroque beauty has another claim it would rather shake, one that made its name synonymous with appeasement. On Sept. 30, 1938, when the perils posed by Adolf Hitler were already apparent, British Prime Minister Neville Chamberlain, French Premier Edouard Daladier, and Italian leader Benito Mussolini signed the Munich Pact, which handed Nazi Germany large parts of Czechoslovakia in the name of peace.

There's an unwritten rule among serious historians and journalists: No one and nothing should be compared to Hitler and the Third Reich, a singular personality and episode of evil. No direct comparison is reasonable or useful. Russians suffered more fatalities than any other people from what became known as the "Munich Betrayal" and the world war that was to come.

Still, there is a Munich lesson for how to respond to Putin today. Appeasement's price is always high. It encourages malevolent actors to escalate their ambitions as they calculate what they wish to achieve against reduced risk and resistance.

Russia's invasion of Georgia in 2008, and the de facto annexation of its two breakaway provinces, was followed by the illegal annexation of Crimea in 2014, the first forceful changing of European borders since World War II. Then there was Moscow's intervening in Syria to prop up murderous dictator Bassar al Assad in 2015, which was followed by Russia's interference in the 2016 U.S. elections.

Western intelligence services – mostly caught by surprise by these events – have been gaming what the Russian leader might do next. It was a safe bet that it would fall within his campaigns to rebuild regional influence or to undermine the United States, its European allies, and their democracies and primary institutions, NATO and the European Union, while blocking their ability to accept new members from Moscow's neighborhood.

Part of the answer came last weekend.

Two aspects of Russia's military action were significant. First, it was the first time that Putin had so brazenly used his own conventional military forces against Ukraine, where he has acted mostly in the shadows or through proxies. Second, by firing upon Ukrainian vessels, he must have factored in a potential chain of events that might have led to a wider war.

President Donald Trump's tweet on Thursday that he wouldn't meet with Putin this weekend on the margins of the G-20 in Argentina was encouraging but insufficient.

In an interview with the German-language Bild Zeitung, Ukrainian President Petro Poroshenko this week warned, "The only language [Putin] understands is the solidarity of the Western world. We can't accept Russia's aggressive policies. First it was Crimea, then eastern Ukraine, now he wants the Sea of Azov."

Here's a brief guide to what has happened and what should be done, providing context and a range of responses recommended by Atlantic Council experts:

In 2003, Russia and Ukraine reached agreement on cooperation in the shared waterways of the Sea of Azov and the Kerch Strait, which runs between Russia and Crimea as the only entrance to the sea.

After Russia illegally annexed Crimea in 2014, it used its new control of both sides of the strait to build a $3.7 billion bridge connecting Crimea to mainland Russia. Its low height of 115 feet cut off access of larger ships to the Ukrainian ports of Mariupol and Berdyansk, resulting in a sharp decline of port revenues.

In May of this year, following the bridge's completion, Russia moved naval vessels, including warships from its Caspian Flotilla, to the Sea of Azov. Since then, Russia has detained some 150 Ukrainian and foreign merchant ships and interrogated their crew members, according to a Ukrainian official and port authorities, deterring more ship traffic and further cutting revenues.

Last Sunday, Russian forces opened fire and seized three Ukrainian naval ships after rebuffing their attempt to travel from the Black Sea to the Sea of Azov through the Kerch Strait. Russian troops detained 24 Ukrainian crew members, six of whom were injured, and have now transferred them to Moscow for criminal prosecution.

The United States, European allies, the European Union, and NATO have condemned the Kremlin's aggression against Ukraine. Without more than that, however, Putin won't be deterred.

Atlantic Council experts favor a three-pronged, diplomatic, economic, and military response, including but not limited to the following:

- Diplomatically, the U.S., NATO, the EU, and other western allies should not only condemn the Russian actions but also detail how they violate specific international conventions. There should be demands that Russia apologize, punish those responsible, and immediately release the Ukrainian sailors.

Russia should permit Ukrainian shipping free access to the Sea of Azov, in accordance with the 2003 agreement. The NATO and EU should jointly send a fact-finding mission to the Sea of Azov.

- Economically, the United States and Europe should more stringently enforce the already existing sanctions imposed following Russia's annexation of Crimea, since that is the source of the problem. They should then prepare new sanctions on Russian financial institutions and shipping interests, to be implemented if Russia doesn't reverse course.

To impose even greater costs, the U.S. should push Germany to suspend the ill-conceived Nord Stream 2 gas pipeline from Russia to Germany via the Baltic Sea. Once operational, Nord Stream 2 — which bypasses Ukraine — will cost Ukraine a 3 percent drop in GDP. Russia's multiple provocations undermine European efforts to obtain guarantees of continued gas transit through Ukraine after Nord Stream 2 comes on line.

- Given the more direct Russian military involvement, it's also time to increase surveillance and other monitoring of the Sea of Azov by the Organization for Security and Co-operation in Europe and Western drones. A stronger message would be to widen NATO and U.S. military presence in the eastern Black Sea by increasing freedom of navigation operations.

Finally, the U.S. and allies should provide additional defensive naval armaments to Ukraine, including coastal defense surface-to-ship missiles, patrol boats, radar, and additional intelligence, surveillance, and reconnaissance assets.

Critics might argue that such actions would be provocative. History has taught us, however, that appeasement is the most inflammatory action.

That is the lasting lesson of Munich.

Frederick Kempe is a best-selling author, prize-winning journalist and president & CEO of the Atlantic Council, one of the United States' most influential think tanks on global affairs. He worked at The Wall Street Journal for more than 25 years as a foreign correspondent, assistant managing editor and as the longest-serving editor of the paper's European edition. His latest book – "Berlin 1961: Kennedy, Khrushchev, and the Most Dangerous Place on Earth" – was a New York Times best-seller and has been published in more than a dozen languages. Follow him on Twitter @FredKempe and subscribe here to Inflection Points, his look each Saturday at the past week's top stories and trends.

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