The abrupt firing Tuesday of Secretary of State Rex Tillerson follows months of infighting between the State Department and White House over efforts by Tillerson to save the Iran nuclear deal and ignore President Donald Trump’s demands that the agreement be fixed or completely scrapped by the United States, according to multiple sources with knowledge of the situation who spoke to the Washington Free Beacon.

In the weeks leading up to Tillerson’s departure, he had been spearheading efforts to convince European allies to agree to a range of fixes to the nuclear deal that would address Iran’s ongoing ballistic missile program and continued nuclear research.

While Trump had prescribed a range of fixes that he viewed as tightening the deal’s flaws, Tillerson recently caved to European pressure to walk back these demands and appease Tehran while preserving the deal, according to these sources. The Free Beacon first disclosed this tension last week in a wide-ranging report.