Donald Trump met with Volodymyr Zelensky and a large group of European leaders who descended on the White House Monday to support Ukraine’s president, bracing for the possibility of another explosive series of meetings that could change the course of his country’s future.

Ukrainian President Volodymyr Zelensky said he was thankful over a dozen times during public remarks with President Trump at the White House on Monday. Trump had criticized Zelensky during a previous meeting in February for not expressing sufficient gratitude.

A few of the leaders were said to have interrupted summer holidays to fly to the United States on less than 24 hours’ notice to meet with the Ukrainian leader.

It is quite possible that Monday's meeting in the White House could prove even more crucial to the future of Ukraine - and for all of Europe's security - than last Friday's US-Russia summit in Alaska. On the surface, that Putin-Trump reunion seemed to live down to every expectation.