China’s People's Liberation Army Navy (PLAN) sent a carrier battle group formed around the aircraft carrier CNS Liaoning in the Miyako Strait, between Japan and Taiwan, on April 4, 2021. The group will carry out an exercise to “help build the capacity to protect national sovereignty, security and development interests," according to the Navy. As one of the main entries from the East China Sea into the Philippine Sea, the Miyako Strait is crucial for China.

The Liaoning was commissioned by the PLAN in 2012. Designated Type 001, it is capable of carrying 40 aircraft including a wing of 26 J-15 fighter jets, the Chinese version of the Russian Su-33. 

The same day, an aircraft carrier strike group of the US Navy led by the USS Theodore Roosevelt entered the South China Sea from the Strait of Malacca. Theodore Roosevelt’s Carrier Air Wing Eleven is composed of nine squadrons, including four strike fighter squadrons of F/A-18F Super Hornet. “It is great to be back in the South China Sea to reassure our allies and partners that we remain committed to freedom of the seas,” said Doug Verissimo, the commander of the Carrier Strike Group.

The deployment of the two carrier groups in the East and South China Seas takes place at a time of heightened territorial tensions in the region. Taiwan is a point of contention between the two powers. The Taiwanese Ministry of National Defense reported that the Chinese People's Liberation Army Air Force (PLAAF) flew about 380 sorties into the country’s ADIZ in 2020, the highest since 1996. The surge in activity was attributed to the warming of the relationship between the island country and the United States. 

Throughout Donald Trump’s presidency, over ten arms sales were concluded between the two nations. The stance of the United States is expected to remain the same during Joe Biden’s term. “We will continue to assist Taiwan in maintaining a sufficient self-defense capability,” said US State Department spokesman Ned Price in a statement. “Our commitment to Taiwan is rock-solid and contributes to the maintenance of peace and stability across the Taiwan Strait and within the region.”

Following news of the Chinese deployment on April 4, 2021, the JS Suzutsuki destroyer of the Japan Maritime Self-Defense Force, along with maritime patrol aircraft, was sent to monitor the battle group.

Japanese Prime Minister Yoshihide Suga declared Taiwan’s peace and stability were key to the region and that Japan would cooperate with the United States to calm rising tensions between China and Taiwan. Suga is to meet with Biden by the end of April 2021.

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Chinese military aircraft entered the Taiwanese airspace twice in two days, prompting Biden’s administration to voice its support vis-a-vis Taiwan’s sovereignty
 

On March 27, 2021, the Philippine Minister of Defense Delfin Lorenzana announced the deployment of both air and sea assets to monitor a fleet of 180 to 200 fishing vessels near Julian Felipe Reef suspected of belonging to the People’s Armed Forces Maritime Militia (PAFMM). The Chinese maritime militia has been used as an informal force for Beijing to secure maritime assets in the region.

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The Philippine Air Force was sent to monitor 180 to 200 fishing vessels suspected of belonging to the Chinese maritime militia near Julian Felipe Reef.