Despite a chorus of critics that’s likely to grow, Richard Grenell will do well for America in his new role as acting Director of National Intelligence. That’s my prediction from covering the United Nations during the years when Mr. Grenell served as spokesman for the United States mission to the world body.

Mr. Grenell was hardly the press pool’s favorite. Then again, too, he never came to Turtle Bay to make friends. He was a prickly, tough, tireless, and always capable amanuensis for the seven ambassadors whom he served. He endlessly promoted President George W. Bush’s agenda during a challenging period to advocate for America’s foreign policy in the international forum.

Reporters at the United Nations often complained about Mr. Grenell. He called them angrily when a critical article or a broadcast piece was issued. He demanded corrections even when he knew none was likely to be forthcoming.

The UN at the time was at loggerheads with Washington. Secretary General Kofi Annan publicly declared America’s expedition in Iraq “illegal,” even while his own administration of the United Nations was embroiled in scandal, most notably the corrupt Iraq program known as Oil for Food.

Mr. Grenell, unlike others in his position, was never shy about siding with America, even at the risk of angering Turtle Bay mandarins and their American cheerleaders.

As The New York Sun’s UN correspondent during those years, I experienced all sides of Mr. Grenell. At first he ignored me, then — a few times — berated me, and finally helped and befriended me. We kept in touch since he left Turtle Bay, as I was watching his accession to the American ambassadorship in Berlin, whence he was one of Mr. Trump’s most effective envoys in Europe.

There were, of course, those who take a dimmer view of Mr. Grenell. Reuters’ reporter here in Turtle Bay, Irwin Arrief, who often clashed with Mr. Grenell, was quoted by a Washington Post columnist, Max Boot, as saying that Mr. Grenell is “the most dishonest and deceptive press person I ever worked with.”

Yet, more than any spokesman before or after him, Mr. Grenell made himself available to the press corps, arranged frequent briefings with Yankee diplomats, and was always available to answer questions. “No US spokesman since he left was so engaged with the press,” says one official here.

Mr. Grenell quickly made powerful enemies when, in May 2018, he arrived at Berlin. Germany’s left wing press and other establishment types dubbed him the most undiplomatic of all diplomats. At the same time he managed to make German politicians uncomfortable over their positions on fundamental disagreements between Europe’s most consequential country and America.

A national hawk who honed his talons alongside John Bolton, Mr. Grenell’s nursed pet peeves that often resembled those of Mr. Trump, who often praised him. Senior ambassadors are often only as effective as their perceived relation with the commander in chief. Being frequently praised by the president helps establish credibility.

One of Mr. Grenell’s early successes was getting Berlin to ban Iran’s terrorist-supporting Mahan airline from operating in the country. Last December the Bundestag also voted on a resolution calling on Chancellor Merkel to designate Hezbollah as a terror organization in its entirety (currently Berlin only designates the Lebanon-based organization’s “military wing” as such, while giving a pass to the “political wing.” Hezbollah’s chief, Hassan Nasrallah, for one, had denied such a distinction exists.)

Mr. Grenell remains opposed to Germany’s participation in Russia’s Nord Stream 2, a project that could potentially make Europe dependent on Moscow for its energy needs. Similarly, he’s pushed one of Mr. Trump’s top goals, calling on Germany to increase its financial contributions to NATO. Under pressure, Ms. Merkel is on record saying she is working toward raising contributions, but Mr. Grenell keeps pushing for action.

Shortly after arriving in Berlin, Mr. Grenell scored his first success, where previous ambassadors failed. He got Berlin to ask the United States for extradition of a Nazi prison guard, Jakiw Palij, a Queens resident at the time. Mr. Grenell also became a tireless pro-Israel advocate, fighting against the Boycott, Divestment and Sanctions movement’s attempts to overcome Europe.

In the last few months, Mr. Grenell widened his activities beyond Germany, negotiating a direct-flight agreement between Serbia and Kosovo and working toward establishing formal relations between the former enemies.

Washingtom critics claim Mr. Grenell has no experience in intelligence or diplomacy. His record shows otherwise. Mostly, Mr. Grenell managed to, so far, stay on Mr. Trump’s good side, and by all accounts the president admires him. In today’s Washington that is no small a recipe for success.