The 2016 NATO summit began in Warsaw on July 8, with leaders from around the alliance gathering for two days of high-level meetings, The Guardian reported. Discussions are likely to focus on countering Russian aggression in Eastern Europe, the global fight against terrorism and the war in Afghanistan, among other things. The Brexit referendum is also likely to be on the minds of many of those attending the summit, and British leaders are trying to make clear that the vote will not affect the United Kingdom's contribution to the alliance. U.S. President Barack Obama called the summit the most important moment for NATO since the Cold War ended, while NATO Secretary-General Jens Stoltenberg said Russia's military actions in Ukraine changed the security environment in Europe. Seeking to reassure Eastern European NATO member states, four countries — the United States, the United Kingdom, Germany and Canada — have agreed to lead multinational deployments in Estonia, Latvia, Lithuania and Poland. A spokesman for the Kremlin said Russia would be closely watching the summit.