Secretary of State Marco Rubio is traveling this week to a gathering of top diplomats from NATO countries.

As Western leaders congratulate themselves for their speedy and severe responses to Russia’s invasion of Ukraine, they’re also scratching their heads with uncertainty about what their actions will accomplish.

The failure of last week’s high-stakes diplomatic meetings to resolve escalating tensions over Ukraine has put Russia, the United States and its European allies in uncharted post-Cold War territory.