It was reported when John Bolton left the national security adviser’s post that the fiery foreign policy guru is no shrinking violet, that he wouldn’t sit quietly by while Donald Trump trashed him.

Trump said he fired Bolton, who then said he resigned. Trump said his decision to let Bolton go was over differences in how to handle Middle East policy.

OK, but now Bolton has become a key player in this impeachment inquiry. You see, we don’t know what Bolton might have heard when Trump was dealing with Ukrainian President Volodymyr Zelinskiy and whether he sought foreign government help for personal political purposes.

It is now assured that Bolton will speak to congressional committees about what he knows and what he saw and heard while serving in the White House. I am one American — who, by the way, doesn’t think much of Bolton’s world view — who is awaiting what he has to say.

My hunch is that he won’t shy away one bit from providing whatever information he has about the president. House committee members already have gotten an earful from other former Trump administration officials, notably from one-time Ukraine envoy William Taylor, who reportedly has said that Trump did withhold military assistance to Ukraine in exchange for a political favor.

Will the former national security adviser’s deposition support that assertion? Will he add more grist for the impeachment mill? John Bolton doesn’t strike me as a shrinking violet. He is a tough guy clothed in a business suit.

If I were a betting man, I would wager that those close to Donald Trump are seriously worried about what John Bolton is going to say about how the president has violated his oath of office.