Squire Patton Boggs has hired Mark Esper, the former US secretary of defence who was fired by Donald Trump, as a senior advisor. 

Esper, who is not a lawyer, has joined the firm in Washington DC, where he will advise its clients on matters including national security, domestic and foreign policy.

“In order to serve clients with complex national security needs, it is critical to have a premier team,” said Squire Patton Boggs ' chair and global CEO, Mark Ruehlmann. “Secretary Esper's addition bolsters our position as a compelling destination for clients who confront a sharp increase in national security challenges resulting from an increasingly turbulent geopolitical environment.”

Esper became the defence secretary in July 2019 after his predecessor, Jim Mattis, resigned in protest following Trump's announcement he would pull US forces out of Syria. Esper was the secretary of the Army at the time of his confirmation by the US Senate.  

He was fired by Trump in November the following year, just days after Trump lost the 2020 US presidential election to Democrat Joe Biden. The pair had been at odds on a number of issues, including Esper's insistence during the Black Lives Matter protests in the summer of 2020 that there were no legal grounds to deploy active-service troops on the streets of US cities, according to the Guardian.

Esper has since been a sharp critic of the former Republican president, describing his as a "threat to democracy". 

In a statement, Esper said of his move to Squire Patton Boggs: “We are living through an era of great change that has stoked national security ramifications that are rippling through board rooms around the world. Squire Patton Boggs has a clear vision to lead in this space and I am excited to add to the unique offering that the firm is building.”

His arrival follows other recent hires the firm has made to strengthen its offering in international trade, national security and international investigations, including DHS assistant secretary Bridget McGovern, former US ambassador Paul Jones, deputy assistant to the president for international economic affairs Everett Eissenstat and US Department of Treasury official Adam Hensel-Briscoe. 

Last November the firm also hired a team of national security legal professionals in Washington DC with experience handling economic sanctions enforcement and matters requiring US government approvals from Stroock & Stroock & Lavan. 

Esper currently serves as chairman of the national security practice at venture capital firm Red Cell Partners and will continue in that role alongside his new position at Squire Patton Boggs.