During a May 10 meeting with Russia's Foreign Minister Sergei Lavrov and Ambassador to the U.S. Sergey Kislyak, Trump began describing details about an Islamic State terror threat, according to current and former U.S. officials. (The Washington Post)

On Monday night, The Washington Post reported that President Trump revealed highly classified information to the Russian foreign minister and ambassador during a meeting at the White House. Specifically, he is said to have described the details of an Islamic State threat related to the use of laptop computers on aircraft. The information itself was reportedly provided by a close Middle Eastern ally.

Much of the controversy has to do with the fact that Trump allegedly provided the information to Russia, a U.S. adversary with which he and some of his associates have alleged ties. However, in doing so, he also set back U.S. counterterrorism efforts against the Islamic State as well as al-Qaeda and other terrorist groups.

The immediate damage

Intelligence officials are usually very careful not to reveal “sources and methods” — the sources of information, and the methods used to collect it. This is for obvious reasons. If the identity of a person who was the source of clandestine information is revealed, then that person’s life could be put at risk. Similarly, if the methods used to gather information secretly are revealed, then adversaries may be able to protect against them in the future. This is why people have been asking whether the president compromised the sources and methods used to collect the intelligence he shared.

National security adviser H.R. McMaster said, “At no time were any intelligence sources or methods discussed and no military operations were disclosed that were not already known publicly.” However, this narrow denial does not discount the possibility that information was disclosed that could enable Russia to infer the sources and methods through which information was acquired. By revealing the city where the information was collected, he also may have enabled Moscow to determine the ally that provided it.

The most direct and immediate impact may be to jeopardize a critical source of intelligence on the Islamic State, thereby making it more difficult to detect and thwart terrorist plots. It is also possible that Moscow could use the information to its advantage in various ways that harm the United States or its allies.

As bad as the exposure of sources and methods would be on its own terms, the long-term consequences for counterterrorism are even worse. This is because Trump divulged information collected by a U.S. ally, without its permission. This was a breach of trust that is likely to damage not only the intelligence relationship with the country in question, but also with other countries.

The U.S. relies heavily on allies for counterterrorism information

 Most intelligence work focuses on gathering and analyzing information and presenting it to policymakers so they can make educated decisions.

Counterterrorism intelligence is different. It requires identifying and thwarting threats before they happen. Analysis and operations go together in preventing an attack or neutralizing a threat. The United States cannot do this by itself — this effort relies heavily on intelligence cooperation from other countries.

Intelligence cooperation on counterterrorism takes various forms. Simple cooperation involves the exchange of single pieces of intelligence, often regarding a common target such as the Islamic State.

There are also more complex forms of cooperation. For example, the United States has often bartered technical information gathered from satellites and other sources gleaned through technical means, for human source reporting that is more difficult to acquire. Sometimes, partners provide intelligence as part of a broader effort to maintain positive relations with the United States. Intelligence cooperation sometimes extends beyond the exchange of information to include the conduct of joint operations.

Despite vastly increasing the budget for the intelligence community in general and counterterrorism intelligence specifically after the attacks of Sept. 11, 2001, the United States relies heavily on intelligence cooperation from other countries to fight terrorism. The information the United States collects via technical means can be frustratingly inconclusive and is often much more useful if paired with human intelligence. Partner nations are often better positioned to collect intelligence on their own soil and to act on that intelligence when necessary.

This is partly because of numbers. Even after going on a hiring binge, the United States still does not have enough intelligence officers to cover all the ground necessary. Partner intelligence services also often know the local language, including various dialects; share the ethnic and historical ties to intelligence targets; and understand the cultural terrain in ways that most U.S. intelligence officers never could.

Local intelligence services are often the first line of defense when it comes to disrupting attacks like the one the Islamic State may have been planning with laptop computers on aircraft. Intelligence relationships also help track foreign fighters, target key nodes in terrorist networks, and sever links between terrorist groups. Because not every terrorist is killed on the battlefield, partner services are also critical for interrogating and incarcerating suspected terrorists and determining whether U.S. investigators will have access to them.

Trump’s revelation could seriously damage cooperation with numerous countries

Most intelligence cooperation takes place bilaterally — between one country and another — rather than among a group of countries. Anytime a country shares intelligence, it risks exposing sources and methods. By limiting the exchange to one recipient, the intelligence service providing the information can limit this exposure and make calculated assessments about what to share.

This is why Trump’s decision to reveal classified intelligence to Russia could be so damaging in the long run. It was not the United States’ to provide. According to the rules of the intelligence game, to share this information, the United States would need permission from the country that collected it. Because the partner in question had not consented, the president violated a cardinal rule of intelligence cooperation.

The ally that provided the information reportedly warned U.S. officials repeatedly that it would cut off access to this type of intelligence if it were shared too widely. Other countries will have taken note, too. If the reporting is correct that Trump provided this information in an impulsive and boastful manner, the situation may be even worse. Leaks in an intelligence apparatus can be plugged. There is no recourse when it is the president, who has a right to every piece of data shared with the United States, who is the source of the problem.

Just like traditional alliances, some intelligence relationships are deeper and more durable than others. Sharing a common terrorist threat can help facilitate closer cooperation. However, if an intelligence relationship is characterized by mistrust, this can complicate cooperation even if both countries both give the same threat a high priority. Often, intelligence cooperation is insulated from the ups and downs of ordinary diplomatic relations, as long as both sides benefit from it. But trust is essential.

After Monday night, countries worldwide will be rethinking the merits of intelligence cooperation with the United States. The negative ramifications will be felt throughout the U.S. intelligence community, but counterterrorism is likely to be among the hardest hit.

Stephen Tankel is an assistant professor at American University and an adjunct senior fellow at the Center for a New American Security. He previously served as a senior adviser for Asian and Pacific security affairs at the Defense Department. You can follow him on Twitter at @StephenTankel.