The final scheduled hearing in the House’s impeachment inquiry was Thursday, with former National Security Council Russia expert Fiona Hill and Ukraine diplomat David Holmes testifying.

Below are some key takeaways.

1. Holmes’s succinct explanation of two quid pro quos

The explanation by Gordon Sondland, the U.S. ambassador to the European Union, of how the Ukraine quid pro quos worked got lots of attention Wednesday — remember “2 plus 2 equals 4?” Sondland’s point was basically that everyone understood why a White House meeting and military aid were being withheld, even if President Trump never explicitly told him to convey a quid pro quo.

But Holmes even more methodically and succinctly laid out how the quid pro quos worked, and how they allegedly would have been understood by the Ukrainians to include not just a White House meeting but also military aid.

“Sir, we’ve been hearing about the investigations since March — months before — and President Zelensky had received a congratulatory letter from the president saying he would be pleased to meet him following his inauguration in May,” Holmes said. “And we had been unable to get that meeting. And then the security hold came up with no explanation.”

Holmes added: “And I’d be surprised if any of the Ukrainians — we discussed earlier, you know, they’re sophisticated people — when they received no explanation for why that hold was in place, they would have drawn that conclusion.”

Republicans have argued that there could not be a quid pro quo, because Ukraine may not have known for weeks about the hold on military aid and because it was eventually released without any Ukrainian announcement of Trump’s desired investigations.

There are still questions about just how early Ukraine might have known, though, including after Laura Cooper’s testimony Wednesday. In addition, the aid was released Sept. 11 — after the hold was reported publicly and amid bipartisan pressure on the administration to do so. It was also six days after The Washington Post editorial board reported it had been “reliably told” that Trump was “attempting to force Mr. Zelensky to intervene in the 2020 U.S. presidential election by launching an investigation of the leading Democratic candidate, Joe Biden.”

In other words, as Philip Bump wrote, if this was indeed used as leverage, there were plenty of reasons the gambit would have been scrapped.

2. GOP questions backfire

As any lawyer will tell you, you’re not supposed to ask a witness a question if you don’t know how they’ll answer. That happened over and over again with Republicans on Thursday — thanks in large part to two very capable witnesses who weren’t willing to go along with the GOP’s lines of questioning.

The most telling example came when the top Republican on the House Intelligence Committee, Rep. Devin Nunes (R-Calif.), tried to establish the premise that the “black ledger” Ukraine shared on former Trump campaign chairman Paul Manafort wasn’t credible.

Holmes declined to grant that premise, though, and seemed to have done his homework:

NUNES: And the black ledger — is that seen as credible information?
HOLMES: Yes.
NUNES: The black ledger is credible?
HOLMES: Yes.
NUNES: Bob Mueller did not find it credible. Do you dispute what Bob Mueller’s findings were? They didn’t use it in the prosecution or in the report.
HOLMES: I’m not aware that Bob Mueller did not find it credible. I think it was evidence in other criminal proceedings. Its credibility was not questioned in those proceedings. But I’m not an expert on it.

Similarly, Holmes cut in when GOP counsel Stephen Castor asked him about a review that was conducted of how much European allies gave in aid to Ukraine. Castor’s idea was apparently to suggest Trump was concerned about burden-sharing when he withheld the military aid, rather than personal politics.

But Holmes interjected to note that the review happened after — and he emphasized that word — the Ukraine money was held up.

Then he added that the findings were “illuminating”: “The United States has provided combined civilian and military assistance to Ukraine since 2014 of about $3 billion plus … three $1 billion loan guarantees — those get paid back, largely. So just over three-billion dollars. The Europeans, at the level of the European Union plus the member states combined since 2014, my understanding have provided a combined $12 billion to Ukraine.”

The retort was clear: Castor’s argument was pretty nonsensical.

When questioning Hill, Castor tried established some background by asking questions that would usually elicit very brief answers. But she often provided very detailed ones that took things in a very different direction.

One came when Castor seemed to be trying to poke holes in Sondland’s testimony. He asked about disputes between the two of them, and Hill turned it into an answer about how correct Sondland’s testimony was.

“Now I actually realize, having listened to his deposition, that he was absolutely right — that he wasn’t coordinating with us because we weren’t doing the same thing that he was doing,” Hill said.

She added: “Because he was being involved in a domestic political errand. And we were being involved in national security, foreign policy. And those two things had just diverged. So he was correct. And I had not put my finger on that at the moment, but I was irritated with him and angry with him that he wasn’t fully coordinating. And I did say to him, Ambassador Sondland — Gordon — I think this is all going to blow up. And here we are.”

It was another big moment for Democrats, brought to you by Republicans on the committee.

3. Hill pushes back on Ukraine conspiracy theories — hard

Pretty much every witness, up to and including Sondland in his blockbuster testimony Wednesday, has been reluctant to craft a narrative or be overly combative with lawmakers.

Hill didn’t appear to have any such reservations.

In her opening statement, she made clear that she would take on the conspiracy theories that Republicans, including those on the committee hearing her testimony, have been pushing about Ukraine’s alleged interference in the 2016 U.S. presidential election.

“Based on questions and statements I have heard, some of you on this committee appear to believe that Russia and its security services did not conduct a campaign against our country — and that perhaps, somehow, for some reason, Ukraine did,” Hill said. “This is a fictional narrative that has been perpetrated and propagated by the Russian security services themselves.”

She added: “In the course of this investigation, I would ask that you please not promote politically driven falsehoods that so clearly advance Russian interests.”

Nunes offered a preemptive rebuttal of Hill’s opening statement, arguing that Republicans were not suggesting that Russia did not interfere but that, perhaps Ukraine did as well. (Trump, it bears noting, has suggested it was really only Ukraine.) “Needless to say, it is entirely possible for two separate nations to engage in election meddling at the same time,” Nunes said.

Later in the hearing, though, Hill offered an extensive response to that idea, arguing Ukraine’s actions were simply not at all comparable to what Russia did, given Russia’s was an extensive, top-down effort that included a misinformation campaign. And indeed, she said Ukraine’s actions weren’t terribly dissimilar from officials in other countries who assumed Hillary Clinton would win the election and that they could criticize Trump.

“There’s a whole host of ambassadors from allied countries who tweeted out or had public comments about the president as well,” she said. “And it did not affect security assistance, having meetings with them. If it would, there’d been a lot of people he wouldn’t have met.”

There seemed to be a reason Democrats saved Hill for last (she was initially scheduled to testify alone). Despite having departed her White House position over the summer — before some of the key events in question in the impeachment inquiry — her previous deposition suggested that she was willing to color her testimony and be combative. And that was certainly the case Thursday.

The surprise was that Holmes was just as up to the task.

4. Trump tweets at a witness — again

For the second time in six days, Trump tweeted about a witness as the person was testifying.

Holmes’s key testimony regards Sondland’s conversation with Trump on July 26, the day after Trump’s call with Ukrainian President Volodymyr Zelensky. Holmes testified that he overheard Trump and Sondland talking about investigations. After the conversation, Holmes said, Sondland told him that Trump didn’t care about Ukraine but only about the investigations he was seeking.

“While Ambassador Sondland’s phone was not on speakerphone, I could hear the president’s voice through the earpiece of the phone,” Holmes said. “The president’s voice was very loud and recognizable, and Ambassador Sondland held the phone away from his ear for a period of time, presumably because of the loud volume.”

Trump tried to cast doubt on that Thursday morning, shortly before Holmes delivered his opening statement, suggesting that Holmes’s account doesn’t make sense.

“I have been watching people making phone calls my entire life. My hearing is, and has been, great,” Trump said. “Never have I been watching a person making a call, which was not on speakerphone, and been able to hear or understand a conversation. I’ve even tried, but to no avail. Try it live!”

Trump was rebuked — even by Republicans — for criticizing former ambassador to Ukraine Marie Yovanovitch during her testimony Friday. Yovanovitch was asked about it during the hearing and stated that she found it intimidating.

5. Where’s John Bolton?

Some saw Hill as a proxy for former national security adviser John Bolton, under whom she served in the White House and whose potential testimony still hangs over these proceedings. Bolton has said he wants the courts to weigh in on whether he should testify, but Democrats aren’t subpoenaing him because they say it would take too long.

Bolton’s lawyer thickened the plot recently by writing a letter to the House noting that Bolton has knowledge of “many relevant meetings and conversations” that had not, as of Nov. 8, been discussed in the impeachment inquiry. Bolton’s exit from the White House was acrimonious, too, suggesting that he might be a motivated witness if he does appear.

Hill’s testimony only seems to reinforce how significant a witness Bolton could be. He was advising her to register her concerns, and according to her and other witnesses, he was among the most concerned about the metaphorical “drug deal” that was being cooked up with Ukraine.

Bolton may have been hoping that Hill would speak for him, to some degree, and that he wouldn’t have to testify. Expect plenty of talk after this hearing about whether Bolton could build on the foundations of the case that have been laid by Sondland and Hill.