A decade ago in Berlin, a well-informed source cautioned me, half tongue-in-cheek, against holding meetings in a certain hotel not far from the Brandenburg Gate. It seems that a U.S. trade delegation had stayed there not long before and prepared a negotiating strategy late into the night, only to sense in talks the next day that, as my friend put it, "It was as if the Germans had been a fly on the wall the previous evening."

Nations spy on each other. Allies spy on allies, too, even if they don't like to admit it. The United States, France and Israel may lead the pack in this regard, but even Germany spies on its friends, the United States included. In his book "Spies Among Us," former National Security Agency intelligence analyst Ira Winkler explains, for example, that Germany's BND - the federal intelligence service - gathers information on the United States and other foreign business competition for the benefit of German companies.

So why the German furor and dismay over U.S. snooping in Berlin? The outrage somewhat echoes Capt. Renault in the movie "Casablanca" ("I'm shocked, shocked to find that gambling is going on here!").

First, throw the Germans a bone. The leaks from former NSA contractor Edward Snowden about the agency's extensive operations in Germany, the public disclosure that we were monitoring Chancellor Angela Merkel's phone and the recent arrest of one agent for spying for the United States with a second under investigation is a lot to absorb in a short amount of time.

In addition, Germany is exceptionally sensitive about these things. Surveillance was the backbone of Nazi tyranny. The treachery continued for 40 years in Communist East Germany. By some estimates, a half-million informants ("inoffizielle Mitarbeiter") spied for the secret police, the Stasi, on fellow citizens in the German Democratic Republic. According to one Stasi colonel, the figure was closer to 2 million if occasional informants were included. This was in a country of 17 million.

It was in this context that German President Joachim Gauck gave an angry TV interview in which he said of U.S. behavior, "Enough is enough." Gauck is the son of a Soviet gulag survivor. In East Germany, he was a Lutheran minister turned anti-Communist civil society activist. After German unification, Gauck spent a decade in charge of the Stasi files, overseeing the opening of millions of dossiers that exposed in excruciating detail the reach of the surveillance state. Indeed, some Germans have a visceral reaction to these things. Merkel, too, comes from the East.

But a second major factor helps explain the intensity of the German debate. Allies spy on each other according to their capabilities - and the United States' capabilities dwarf those of Germany. This stings, especially for a country with a unique America complex.

Throughout the Cold War, West Germany was the United States' junior partner. In contrast, France was never divided, had nuclear weapons and maintained an independent foreign policy. Did Germans never notice? Dependency breeds resentment, even in the closest of families. An editor at the conservative daily Die Welt once told me, "We Germans have never fully forgiven you Americans for freeing us from fascism when it was something we couldn't do for ourselves."

This autumn, Germany will mark 25 years since the fall of the Berlin Wall. We forget that united Germany is still young and very much a work in progress. What's more, our relationship with Berlin is more fragile, the terms more fluid, than many think. In one recent poll, after six years of President Barack Obama, majorities found the United States aggressive, reckless and power-hungry.

In another recent poll, in reference to the crisis in Ukraine, 45 percent of Germans said they want their country firmly anchored in the West. Forty-nine percent, though, want Germany to play an intermediary role between the West - NATO and the European Union - and Russia.

It's "unsettling," historian Heinrich Winkler told Der Spiegel, when a "strong minority is questioning vital elements of our Western orientation, namely our memberships in NATO and the European Union."

Unsettling indeed.

This should remind us - Atlanticists in the United States and Germany alike - that beyond the spying dust-up we have larger strategic matters to tend to, such as a rising China, increasing Russian belligerence and a dangerously unstable Arab-Persian world. We'll never have Europe as a strong ally unless Germany is healthy and comfortable with U.S. power.

Responsible Germans must do their part. But we Americans must do all we can to diminish German resentment and drift.

Jeffrey Gedmin is a senior fellow at Georgetown University's School of Foreign Service and a former president of the Aspen Institute in Berlin. He wrote this for the Washington Post.