From the South China Sea to the Himalayan Sino-Indian border, and even in one of its own cities, China has doubled down on its claims of territory, and taken a harder line in response to perceived challenges.
And as those disputes escalated this year with renewed and rising tensions, Xi has bulked up the military and increased its budget, with the instruction to "resolutely safeguard national sovereignty, security and development interests."
Here's what you need to know about China's key flashpoints in the Asia-Pacific region.
Why are countries fighting over the South China Sea?
Dotted with small islands, reefs and shoals, the South China Sea is a crucial global shipping route and home to a messy territorial dispute.
Who claims what: China claims it owns almost all of the 1.3 million square mile South China Sea, but at least six other governments also have overlapping territorial claims in the contested waterway: the Philippines, Vietnam, Malaysia, Indonesia, Brunei and Taiwan.
The United States doesn't have any claims in the waters, but has repeatedly challenged China's claims.
China went ahead and built islands anyway: Since 2014, China has turned numerous obscure reefs and sandbars -- far from its shoreline -- into man-made artificial islands heavily fortified with missiles, runways and weapons systems, prompting outcry from the other governments.
The US and its allies have pushed back by sailing warships through the South China Sea close to features claimed or occupied by China, in what it calls freedom of navigation operations (FONOPS). They say such patrols enforce the right of free passage in international waters; China argues these are violations of its sovereignty.
But things are escalating now: The US has stepped up its challenges this year; it formally rejected China's claims as illegal, and sanctioned dozens of Chinese companies for building the artificial islands. In July, two US Navy aircraft carriers conducted joint military drills in the sea for the first time in six years -- a strong show of force.
All this has sparked Chinese fury and escalated tensions; China launched a series of ballistic missiles into the sea, with state-run media warning that "China does not fear a war."
Why this matters: Under international law, whoever owns the contested string of islands in the sea will have the rights to all the resources in its nearby waters like fish, oil and gas. More broadly, whoever controls this sea will also hold power over one of the world's most valuable trading routes -- it hosts one third of all global shipping.
What's the deal with Taiwan?
Taiwan is a self-governing democratic island of around 24 million people, which split from mainland China in 1949 after the end of a bloody civil war.
China insists Taiwan is its territory: Authorities in Beijing claim full sovereignty of Taiwan, even though Taiwan has never been controlled by China's ruling Communist Party. The two sides have been governed separately for more than seven decades.
For years, Beijing has attempted to impose diplomatic,
