Obama used his visit to call for Europeans - particularly young people - to stand up for the ideals of liberty and free determination. Added to this, he criticized the Russian government for acting on the belief that power derives from military force and overt shows of dominance.
During his day in Brussels, he attended an EU-US Summit with Council President Herman Van Rompuy and Commission President José Manuel Barroso, where Ukraine was top of the agenda, alongside the continuing negotiations towards a transatlantic trade agreement.
This was followed by a meeting with NATO Secretary General Anders Fogh Rasmussen, where the two men affirmed NATO's commitment to its allies - seeking to reassure the understandably nervous NATO members who share borders with Russia.
In the evening, President Obama addressed an audience of about 2,000 people in the concert hall at BOZAR, Brussels' Palace of Fine Arts, a striking backdrop for a fighting speech.
Beginning with a grand narrative of history, Obama spoke of the ideals of free will and freedom of conscience that emerged in Europe after centuries of war. Now, these ideals were being tested once more; by the outdated view of power that might makes right.
These ideals, he claimed, are true and universal - the ideals of democracy, open economies, and human dignity. He argued passionately that we should never take progress for granted, and these ideals need to be defended - particularly by the young people of Europe.
Obama spoke about his visit that morning to the First World War Flanders Field Cemetery. To be casually indifferent to the people of Ukraine, he said, would be to ignore the example set by the men buried in those war cemeteries.
After making this rousing case for democratic ideals, Obama directly criticised Russia's conduct in Crimea. Because of these ideals, he said, Russia's violation of international law must be condemned.
This was not, Obama argued, about the West seeking to dominate Ukraine - it had not, and it would not send troops to the country. Nor was this a new Cold War - Russia did not lead a bloc of nations united by ideology.
Instead, the conflict was a clash of ideas about power, with the USA and its allies standing up to Russia's belief that its strength entitled it to act against international law.
So the USA would continue to step up pressure on Russia by isolating the country politically and imposing sanctions.
Obama also renewed NATO's commitment to its members while noting that he was concerned that not all countries were pulling their weight.
Returning to his central point, Obama argued that if principles were backed by courage and resolve, then hope would overcome fear and freedom would overcome tyranny.
An impassioned speech - but it remains to be seen whether indeed the USA and the EU's soft power approach, though backed by worthy ideals and international law, will stop military might as Russia seeks further power.
Hannah O'Kane is currently a trainee at the European Parliament, Research Services DG