The House select committee investigating the Capitol attack has issued subpoenas to six of Donald Trump’s associates involved in the effort to overturn the results of the 2020 election from a “command center” at the Willard Hotel in Washington DC. The subpoenas demanding documents and testimony open a new line of inquiry into the coordinated strategy by the White House and the Trump campaign to stop the certification of Joe Biden’s election win, and whether it was connected to the 6 January insurrection. House investigators on Monday targeted six Trump officials connected to the Willard: the legal scholar John Eastman, Trump’s campaign manager Bill Stepien, Trump’s adviser Jason Miller, the former national security adviser Michael Flynn, Trump’s campaign aide Angela McCallum, and the former New York police department commissioner Bernard Kerik. The select committee chairman, Bennie Thompson, said in a statement that the panel was pursuing the Trump officials in order to uncover “every detail about their efforts to overturn the election, including who they were talking to in the White House and in Congress”. The six Trump officials compelled to cooperate with the select committee may have some of the most intimate knowledge of how the different elements of the former president’s effort to stop the certification – fit together. The subpoenas for Eastman and other Trump associates – first reported by the Guardian – show the select committee’s resolve to uncover the “centers of gravity” from which Trump and his advisers schemed to overturn the election, according to a source familiar with the matter. House investigators are taking a special interest in Eastman after it emerged that he outlined scenarios for overturning the election in a memo for a 4 January White House meeting that included Trump, the former vice-president Mike Pence and Trump’s chief of staff, Mark Meadows. At the meeting, according to a source close to Trump, Eastman ran through the memo that detailed how Pence might refuse to certify electoral slates for Biden on 6 January and thereby unilaterally hand Trump a second term. The former president seized on Eastman’s memo, reviewed by the Guardian, and relentlessly pressured Pence in the days that followed to use it to in effect commandeer the ceremonial electoral certification process, the source said. Trump was not successful in co-opting Pence and Congress certified Biden as president. But House investigators are examining whether the memo was part of a broader conspiracy connected to the Capitol attack – and whether Trump had advance knowledge of the insurrection. The pro-Trump legal scholar also pressured nearly 300 state legislators to challenge the legitimacy of Biden’s win, reportedly participated at a “war room” meeting at the Willard on 5 January and spoke at a rally before the Capitol attack, the select committee said. House investigators also subpoenaed Stepien, the manager of the Trump 2020 campaign, after he urged state and Republican party officials to delay or deny the certification of electoral votes ahead of the joint session of Congress on 6 January. The select committee said it had subpoenaed Miller since he was in close and repeated contact with top Trump associates at the Willard and he too participated in the “war room” meeting that took place the day before the Capitol attack. At that meeting, the select committee said, Trump’s former chief strategist Steve Bannon and Trump’s lawyer Rudy Giuliani discussed how to subvert the election by having Pence follow Eastman’s memo and not certify the election for Biden. The select committee issued further subpoenas to Bernard Kerik, an aide to Giuliani based at the Willard, as well as Angela McCallum, who also pressured state legislators to challenge Biden’s win. House investigators sent a sixth subpoena to Flynn, Trump’s former national security adviser fired in 2017 for lying to the FBI, after he attended an 18 December Oval Office meeting about whether Trump could invoke emergency powers based on lies about election fraud. The select committee was expected to send further subpoenas to Trump officials connected to activities at the Willard, the source said, noting that Thompson had told reporters last week that he had signed about 20 subpoenas that were ready to be issued. In the letters accompanying the six subpoenas, Thompson said Eastman was compelled to produce documents by 22 November and appear for a deposition on 8 December. The other Trump officials have until 23 November to produce documents and have deposition dates later in December. But it was not immediately clear whether the subpoenaed aides would comply with the orders. Other Trump administration aides subpoenaed by the select committee have slow-walked their cooperation, while Bannon ignored his subpoena in its entirety.