In the latest signal NATO is adopting a tougher posture against cyber and electronic attacks, Secretary General Jens Stoltenberg this week said that the defensive alliance will not remain purely defensive.

Stoltenberg told attendees at the Cyber Defence Pledge conference in London, “We are not limited to respond in cyberspace when we are attacked in cyberspace.”

NATO members have already “agreed to integrate national cyber capabilities or offensive cyber into Alliance operations and missions,” he said. But the parameters of a NATO response to cyber attacks remains undefined. In 2015, Stoltenberg said that a cyber attack against one member nation could trigger an Article 5 collective response by all members. Yet only once has a collective response ever been invoked, at the request of the United States following the attacks of September 11, 2001. NATO is a defensive organization, so what an offensive cyber posture looks like remains something of a mystery. An Article 5 response can take many different forms.

That’s the strength of the article, according to NATO Deputy General Secretary Rose Gottemoeller. However, while an Article 5 response can be unpredictable, it must be coordinated, which can be tricky with many different partners in possession of many different capabilities.

At an event in May, Gottemoeller said NATO was in the processes of establishing a new innovation board to “bring together all of the parts of and pieces of NATO that have to wrestle with these new technologies to really try to get a flow of information. Many of you having served in any international institution or government, you know how things can get stove-piped. So we are resolved to break down those stove-pipes, particularly where innovation is concerned,” she said.

NATO is building a cyber command that is scheduled to be fully operational in 2023 and will coordinate and conduct all offensive cyber operations. Until then, whatever NATO does offensively, it will rely heavily on the United States and the discretion of U.S. commanders, according to Sophie Arts, program coordinator for security and defense at the German Marshall Fund, who explains in this December report.

“Yesterday’s remarks indicate that NATO’s leadership is thinking more seriously about buttressing the alliance’s deterrence posture in cyberspace and address threats that fall under the threshold of an Article 5 violation,” she told Defense One.

“This tracks recent shifts in strategy adopted by several NATO allies, including the United States, which integrate offensive cyber operations as an important tool to proactively address growing instances of cyber interference from hostile actors.”

But Arts points out there is no field manual for coordinating cyber offensive operations among individual allies, including big players in cyber like Estonia, the U.K. and the United States, who keep command and control over their assets.

In 2017, Gregory Edwards, then director of infrastructure services at NATO’s communication and information agency laid out what that might look like. “You could make a case-by-case decision” about responding to attacks, he said. “You need to have a policy that says, ‘if our operation is disturbed, we will take a specific action.’ The action will be listed. It will be listed what things the commander is allowed to do in that regard. It will be a specific action.”

At an April meeting of NATO policy planners in Washington D.C., Kiron Kanina Skinner, director of Policy Planning at the U.S. State Department said that NATO policy planners had spent most of their time during the meeting discussing how to coordinate cyber effects and policy.

The issue was competing against traditional NATO concerns and even topics like the Russian military buildup on the border of Eastern Europe. “Today, we didn’t talk about the Eastern flank; we talked about cybersecurity,” she said.

Correction: A previous version of this article misspelled the name of NATO Deputy General Secretary Rose Gottemoeller.