Why do countries sometimes not want to share intelligence on an investigation even if they are allies?

Question

https://www.politico.eu/article/sweden-denmark-germany-nord-stream-investigation-tests-eu-intelligence-sharing-around-the-baltic/

It's a highly sensitive issue. The prosecutor leading the Swedish investigation has already said his country is not interested in signing up to a so-called Joint Investigation Team under the auspices of Eurojust, the EU agency set up to solve cross-border crime.

A spokesman for the Swedish prosecutor’s office said the decision related to “secrecy linked to national security” and declined to comment on the progress of Sweden's investigation. A spokesman for the Swedish security service said the country was “cooperating with both Germany and Denmark in this matter.”

Why do countries sometimes not want to share intelligence on an investigation even if they are allies? They use some vague language, but I am wondering if there's a reason for keeping things secret or not sharing intelligence related to an investigation.

Answer 1

The general reason that a country doesn't share all information with its allies is that the operational standard of information sharing is "need to know." The article asserts

Experts say locally controlled secret underwater sensors and submarines will be key to the investigation, along with intelligence from international partners like the U.S. and the U.K.

While Sweden probably does not expect the US or UK to use the location of sensors and submarines against them, the more people who know a secret the more ways that secret can be compromised. At the moment, we can surmise that Sweden's allies do not have a need to know of where its sensors and submarines are located, so Sweden is not going to share that information. Even if Sweden only provided reports from these intelligence gathering sources and not information about the sources themselves to international investigators, this alone can leak information about the source, not just where it is or was but what its capabilities are. And of course if we're talking about human intelligence (a spy or informant) or high level signals intelligence (like a wiretap in an embassy), just the fact that the information they get from the source is available may be a secret Sweden does not want to share.

In this particular case, another confounding factor is that Sweden is possibly the only major country in the region that hasn't been accused of helping carry out the attack. If Sweden creates a joint venture with Denmark or Germany, Russia can use that to argue that the investigation is biased, at the very least by assuming that Germany or Denmark do not have a reason to try and direct the blame toward Russia. Same for the US/UK if the blame is pointed at them, in theory. The problem isn't so much how much bias would actually exist, but the specter of bias can just as easily make the investigation suspect to the rest of the world.

Answer 2

"We have no eternal allies, and we have no perpetual enemies. Our interests are eternal and perpetual." - Lord Palmerston, future Prime Minister of the United Kingdom, 1848.

A similar quote is attributed to Henry Kissinger, sometimes condensed to "America has no friends, only interests".

Alliances shift over time, sometimes very quickly - look at the history of the Soviet Union in WWII for an example, or Finland's response to that. But information about sources and methods can't be recalled when alliances change.

Even when alliances exist, they rarely represent a perfect alignment of interests. While Eurasia and Eastasia are allied against Oceania, they both want Oceania defeated - but each of them would rather the other footed as much of the bill as possible. Eurasia might want to understate its capabilities to its ally, in hope that it won't be asked to contribute as much; alternately, it might overstate its capabilities and loyalty to the alliance, with the goal of encouraging Eastasia to value it and not look for different partners elsewhere. So they still have reason to withhold information from one another.

Countries may even be simultaneously allies in one arena and rivals in another. The same intelligence sources and methods that collect military information beneficial to both countries in an alliance might also be conducting economic/industrial espionage harmful to the interests of one of those countries. (See the Australia/East Timor bugging scandal for a recent example of this kind of conflict.)

All of these are reasons why countries may be cagey about sharing sources and methods even with their allies, even before getting to the obvious point that the more people who know a thing the easier it is for it to leak to the current enemy.

Answer 3

Because it can lead to intelligence assets being compromised either getting killed/destroyed or no longer being able to provide useful information. This can either be from information that gets leaked by the country they shared it with or loss of assets in the country that they shared it with.

Just because two countries are allies doesn't mean that they don't have intelligence assets gathering information from each other.

As for the idea of the information leaking it can happen because another country has compromised the intelligence services or someone straight out shares it like past presidents have done.