David A. Andelman, visiting scholar at the Center on National Security at Fordham Law School and director of its Red Lines Project, is a contributor to CNN, where his columns won the Deadline Club Award for best opinion writing. Author of " A Shattered Peace: Versailles 1919 and the Price We Pay Today ," he was formerly a foreign correspondent for The New York Times and CBS News in Asia and Europe. Follow him on Twitter @DavidAndelman . The opinions expressed in this commentary are those of the author; view more opinion articles on CNN.

(CNN) While this summit in Helsinki, Finland, may not go down in history alongside the moment Franklin D. Roosevelt gave away Eastern Europe to Joseph Stalin at Yalta, it has to rank as the lowest ever in modern times. It's the worst for all sorts of reasons: zero preparation, zero deliverables, zero understanding of the stakes and the horror it's wreaked on the entire Western alliance, not to mention America's intelligence community, who Donald Trump has now thrown definitively under the bus.

My first East-West summit was in Vienna, Austria, in June 1979 when I watched as Jimmy Carter and Leonid Brezhnev signed the SALT II (Strategic Arms Limitation Talks) agreement -- the second major strategic arms limitation pact between the two superpowers of the United States and the Soviet Union. Their appearance together was very much a carefully choreographed summit of equals. The summit's deliverable was quite clear: an agreement to stabilize the number of nuclear weapons in each nation's ballooning arsenal.

That SALT II never formally went into effect was more a byproduct of the Soviet Union's sudden and ill-advised invasion of Afghanistan later that same year than any real flaw in the complex negotiations that preceded the summit itself. Yet because of the deep understanding of the stakes by both sides, both countries still respected the treaty until a new agreement could come along to replace it.

The Vienna summit bore few other resemblances to Monday's in Helsinki between Donald Trump and Vladimir Putin except for the obvious fact that the two leaders of the American and Russian people again sat across the table from each other.

Indeed, there were so many dissonant notes in Monday's impromptu, ill-prepared and clearly quite ill-advised summit. Virtually every other summit between leaders of the United States and Russia or the Soviet Union has been the culmination of long and detailed negotiations. And the outcomes were invariably a treaty, a lengthy set of understandings or a detailed path forward to clear and important conclusions.

Here there was none of that. In short, this might best be described as a summit of lost opportunities.

Of course, we may never really know exactly what Donald Trump and Vladimir Putin cooked up between them in the two hours they spent closeted alone with only interpreters. Ironically, it happens that Carter and Brezhnev spent 90 minutes alone , only with interpreters, at the United States Embassy in Vienna in 1979. But by then, both sides had agreed to the signing of a treaty that took place that same day and that had been preceded by six years of negotiations.

JUST WATCHED Exclusive: Finland President on Helsinki Summit Replay More Videos ... MUST WATCH Exclusive: Finland President on Helsinki Summit 08:20

What the Helsinki summit has succeeded in accomplishing, largely, is erasing the entire post-Crimea efforts of the West to isolate Russia and treat it as the pariah nation it clearly proved itself to be by seizing at gunpoint the territory of another country. That effort was clearly collapsing, of course, even before both leaders ever arrived in Helsinki.

Donald Trump has spent recent months doing his level best to welcome Putin's Russia back into the fraternity of civilized nations and at the same time drive the hitherto united members of NATO far away from the United States. These countries, previously US allies, are the ones who had expelled Putin from their midst within days of his seizure of the Crimea and incursions into eastern Ukraine.

But what else might Trump have given up in his one-on-one with Putin? Might he, for instance, have agreed to ease back on joint military exercises that give the three NATO nations bordering on Russia in the Baltics some assurance that their own independence won't be tested as Ukraine's still is on a regular basis?

For that matter, what was really accomplished in discussions of Syria? Will Russia pull back its forces, the primary bulwark propping up Putin's favorite Middle East dictator, Bashar al-Assad? Hardly likely. Yet both leaders seemed to come down on the side of helping Israeli Prime Minister Benjamin Netanyahu secure his country's security on the Golan Heights --hardly a major strategic priority for Assad and a point easily conceded.

JUST WATCHED Corker: Putin gained a tremendous amount today Replay More Videos ... MUST WATCH Corker: Putin gained a tremendous amount today 00:52

"We both spoke with Bibi and they would like to do certain things with Syria having to do with the safety of Israel," Trump told the news conference. "Russia and the United States will work jointly (in this regard)." As the Israeli daily Ha'aretz put it , apparently with some pleasure, "the US President paid particular attention to Israel during their summit."

But perhaps even more important than Trump and Putin's bizarre press conference was what they did not say. Trump utterly failed to hold Putin fully, or even remotely, accountable for the election interference that the US intelligence and law enforcement communities have all but confirmed down to the last keystroke.

Instead, Trump stood mutely as Putin challenged Robert Mueller's lawyers to come to Russia and lay out their case. Trump went one giant step further -- refusing , with Putin looking on mutely -- even to endorse his own intelligence community's detailed finding of deep Russian involvement in meddling with America's election processes.

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So what's left now that both leaders are headed back to their own countries? Damage control, certainly, for the leaders of other NATO nations who must now examine ruefully the splintered remains of the carefully constructed doghouse where they'd managed to enshrine Putin since his Crimean adventure. Congressional Republicans must now calculate just how deeply their fragile hold on power is imperiled when voters go to the polls to evaluate their party and its leader in November. And for Trump and Putin, no doubt, victory laps with their own bases cheering them on.