China announced on Thursday that it would establish its first overseas military outpost and unveiled a sweeping plan to reorganize its military into a more agile force capable of projecting power abroad.The outpost, in the East African nation of Djibouti, breaks with Beijing’s longstanding policy against emulating the United States in building military facilities abroad.By establishing an outpost in the Horn of Africa — more than 4,800 miles away from Beijing and near some of the world’s most volatile regions — President Xi Jinping is leading the military beyond its historical focus on protecting the nation’s borders.Together with the plan for new command systems to integrate and rebalance the armed forces, the two announcements highlight the breadth of change that Mr. Xi is pushing on the People’s Liberation Army, which for decades has served primarily as a lumbering guardian of Communist Party rule.A presence in Djibouti would be China’s first overseas logistics facility to service its military vessels since the Communists took power, said David Finkelstein, director of China studies at CNA, an independent research institute in Arlington, Va.“In the grand sweep of post-1949 Chinese history, this announcement is yet another indicator that Chinese policy is trying to catch up with national interests that have expanded faster than the capacity of the People’s Republic of China to service them,” Mr. Finkelstein said.The new facility would enable the navy to live up to a strategy laid down this year by the Communist Party in a major defense document, known as a white paper, that outlined its ambitions to become a global maritime power.China has invested heavily in Djibouti’s infrastructure, including hundreds of millions of dollars spent upgrading the country’s undersize port. It has also financed a railroad extending from Addis Ababa, the capital of Ethiopia, to Djibouti, a project that cost billions of dollars. The country has a population of about 900,000, many of whom live in poverty.Strategically, Djibouti offers an excellent place from which to protect oil imports from the Middle East that traverse the Indian Ocean on their way to China, military experts say. From Djibouti, China gains greater access to the Arabian Peninsula.