"All military units must correctly understand major national security and development trends, and strengthen their sense of unexpected hardship, crisis and battle," Xi said on state-owned Chinese television.
In addition, the leader approved the first military command of 2019, involving more complex training and exercises, according to the South China Morning Post (SCMP).
China's armed forces must "prepare for a comprehensive military struggle from a new starting point," Xi said, adding that "preparation for war and combat must be deepened to ensure an efficient response in times of emergency."
Following the ascension of Xi to the presidency of the Central Military Commission (CMC), a national defense organization of the Communist Party of China, he has consistently urged the PLA to enhance combat readiness.
Earlier this week, the PLA Daily, the official newspaper of the Chinese People's Liberation Army, noted in an article that "there was no time for slacking in war preparation," leading Beijing watchers to note the leader's more strident rhetorical tone.
According to Shanghai-based military expert Ni Lexiong, Xi's "high-profile gestures" may be intended to serve as warnings to Taiwan.
China considers self-governing Taiwan to be part of its territory and claims sovereignty over the island.
Taiwan, however, still bears the name of the pre-communist-era Republic of China, a political group whose territorial control was confined to the island at the conclusion of a civil war in 1949, when the People's Republic of China was established in Beijing on the mainland.
"[They] show how seriously Xi is taking China's military training and its preparations for war, while also flexing its strength," Ni asserted, cited by SCMP.
The new military commands signed by Xi focus on improving combat readiness, troop inspections and resistance exercises, according to Chinese state broadcaster CCTV.
"China is increasing its military training so that it has the best solutions for the worst outcomes, either related to the US or across the [Taiwan] strait," Yue Gang, a retired PLA colonel, told SCMP, suggesting that Xi's desire to enhance military readiness may also be due to political tension between the US and China.
"Over the coming year, the US might use Taiwan and the South China Sea as bargaining chips to get what it wants from China with regards to the trade war," Yue suggested.
"And there is always the possibility of increased independence calls from Taiwan," he added.