President Barack Obama delivered a speech in Brussels on Wednesday in which he denounced Russia’s justifications for the annexation of Crimea. In his first trip to the capital of the European Union, and the headquarters of NATO, the president sought to embolden European countries to stand firm against Russian aggression, as well as to reassure NATO members of U.S. support for the region. 

In his speech, Obama claimed Russia had returned to old ways of thinking.

“Russia’s leadership is challenging truths that only a few weeks ago seemed self-evident,” the president is quoted as saying in the New York Times. “That in the 21st century, the borders of Europe cannot be redrawn with force; that international law matters; and that people and nations can make their own decisions about their future.”

The president dismissed Russia’s claim that it only seeks to protect Russians living in countries outside of the Russian Federation.

"Just because Russia has a deep history with Ukraine does not mean it should be able to dictate Ukraine's future," he said, according to the New York Daily News. "No amount of propaganda can make right something the world knows is wrong.”

Furthermore, the president said European allies, particularly those in NATO, must stand together and honor agreements made to protect each other. He specifically warned European countries that declining defense budgets could be a detriment to their collective security.

"If we have a collective defense, it means everyone's go[ing] to chip in," Obama said.

Declining defense budgets are symptoms of complacency and indifference, the president argued. Prior to his speech Obama visited Flanders Field Cemetery, the burial place of thousands of Americans who died during World War I. With a nod to history he warned against such complacency, saying it would have far-reaching consequences.

“Casual indifference would ignore the lessons that are written in the cemeteries of this Continent,” Obama sad. “It would allow the old way of doing things to gain a foothold in this young century. And that message would be heard, not just in Europe but in Asia and the Americas, in Africa and the Middle East.”

Sources: New York Daily News, New York Times