Defense Secretary Jim Mattis last month objected to using military force to protect border agents on the southwest border, a knowledgeable current U.S. official and a former Defense Department official told The Daily Beast.

But Mattis didn’t object on principle. When the Department of Homeland Security requested the so-called force protection mission from the Pentagon, Mattis declined because he thought he lacked the authority to do so, the current official said.

Mattis’ objection, as of late October, was the genesis of a highly controversial White House memorandum issued late Tuesday explicitly authorizing the potential use of lethal force against the unarmed civilians of the migrant caravan.

DHS wouldn’t take no for an answer, The Daily Beast has learned. Homeland Security went above Mattis’ head in order to get Donald Trump’s chief of staff to secure for them the potentially lethal military force for which immigration hardliners in the administration had clamored.