It would be more surprising if Washington didn’t use a false pretext than if it did. From Helen Cobban at lewrockwell.com:
In a key piece of actual extensive, on-the-ground reporting, the New York Times’s Alissa Rubin has raised serious questions about the official US account of who it was that attacked the K-1 base near Kirkuk, in eastern Iraq, on December 27. The United States almost immediately accused the Iran-backed Ketaib Hizbullah (KH) militia of responsibility. But Rubin quotes by name Brig. General Ahmed Adnan, the chief of intelligence for the Iraqi federal police at the same base, as saying, “All the indications are that it was Daesh” — that is, ISIS.
She also presents considerable further detailed reporting on the matter. And she notes that though U.S. investigators claim to have evidence about KH’s responsibility for the attack, they have presented none of it publicly. Nor have they shared it with the Iraqi government.
KH is a paramilitary organization that operates under the command of the Iraqi military and has been deeply involved in the anti-ISIS campaigns throughout the country.
The December 27 attack killed one Iraqi-American contractor and was cited by the Trump administration as reason to launch a large-scale attack on five KH bases some 400 miles to the west which killed around 50 KH fighters. Outraged KH fighters then mobbed the US embassy in Baghdad, breaking through an outside perimeter on its large campus, but causing no casualties. On January 2, Pres. Trump decided to escalate again, ordering the assassination of Iran’s Gen. Qasem Soleimani and bringing the region and the world close to a massive shooting war.

