The sudden resignation of three senior officials from the US defence department a day after the departure of their former boss, Mark Esper , is likely to create more uncertainty between China and the United States on military affairs, observers say. The former US undersecretary of defence for policy James Anderson, undersecretary of defence for intelligence Joseph Kernan and chief of staff to the secretary of defence Jen Stewart all resigned on Tuesday, according to a statement released by the Pentagon the same day. The White House said Anthony Tata, a retired brigadier general whose nomination for a top Pentagon job was abruptly cancelled in July, would replace Anderson in the defence department, the statement said. Ezra Cohen-Watnick, the former acting assistant secretary of defence for special operations and low-intensity conflict, would replace Kernan, while Kash Patel, a former member of the National Security Council staff, would replace Stewart, it said. US President Donald Trump had earlier announced that Christopher Miller, the director of the National Counterterrorism Centre, would replace Esper as defence secretary. Tata, 61, is a controversial figure who once called former US president Barack Obama a “terrorist leader”. He was nominated by Trump for the position of undersecretary of defence for policy earlier this year, but the confirmation hearing was cancelled at the last minute. Since August, he has been serving as acting deputy undersecretary of defence for policy. A source close to the People’s Liberation Army (PLA) said Beijing was worried that Taiwan might take advantage of the uncertainty in the Pentagon to strengthen its military position. The island’s navy said on Monday that US Marines had begun a four-week training operation to help boost Taiwanese troops’ combat readiness. The PLA described the exercise as a “provocative move that challenged China’s bottom line”. Lu Li-Shih, a former instructor at Taiwan’s Naval Academy in Kaohsiung, said Taipei’s high-profile announcement was probably aimed at a domestic audience, after Taiwan’s President Tsai Ying-wen came under pressure for “backing the wrong horse” in the US presidential election, supporting Donald Trump instead of Joe Biden. “The Tsai administration needs to show the Taiwanese public that Taipei hopes the legacy left by Trump and the current US-Taiwan friendship and political trust can be carried on to the next US president,” Lu said. Trump makes ‘unprecedented’ moves to block transition, say former officials Hong Kong-based military commentator Song Zhongping said it was likely that the US would face a “democratic constitutional crisis” during the transition from Trump to Biden, but its comprehensive system of checks and balances would prevent a military crisis from happening. “Pentagon officials may not have time to deal with military to military exchanges between the US and China during the two-month transition, and some diplomatic and defence issues might be postponed,” Song said. “But maintaining stability in the Indo-Pacific region will remain important.” Collin Koh, a research fellow at the S. Rajaratnam School of International Studies at Nanyang Technological University in Singapore, agreed, saying the command and control structure of the US defence establishment did not allow command leaders to make autocratic decisions. “In the absence of a defence secretary, for whatever duration, commanders are still required to adhere to the guidelines on peacetime deployments,” he said.