A PLANNED FIVEFOLD increase in the staff of the U.S. Cyber Command is indicative of how conflict is moving toward center stage for the military, a domain similar to land, sea, air and outer space. The anticipated growth, described in an article by Ellen Nakashima in The Post last week, is intended to protect the country and its private sector from attack, an urgent mission. But now that the United States is going beyond defense, expanding forces for offensive attack, there’s a crying need for more openness. So far, forces exist almost entirely in the shadows.

The Post reported on plans for creation of three types of forces under the Cyber Command. Two are familiar: “combat mission forces” to serve in parallel with military units and “protection forces” to defend Pentagon networks. A third area is new: “national mission forces” that would seek to head off any threat to critical infrastructure in the United States, such as electrical grids, dams and other potential targets deemed vital to national security. These “national mission forces” are expected to operate outside the United States, perhaps launching preemptive strikes on adversaries preparing to take down an American bank or electric grid. However, senior defense officials told The Post that the forces might respond inside the United States if asked by an authorized agency such as the FBI.

The national mission teams seem to be a response to growing evidence that the United States is being swamped by assaults — espionage, theft and disruption — from abroad. If U.S. forces manage to stop enemies from turning out the lights of a major city or crashing the stock market, they will prove their worth. This is no longer a science fiction fantasy. The attacks are real and happening every day.

What concerns us is not the growth of forces but the way it is happening behind the scenes. The U.S. Cyber Command is a military unit, but its chief, Gen. Keith Alexander, is also director of the National Security Agency, which is part of the intelligence community. So far, operations and deployments are being handled almost entirely in secret.

Aside from a line in a speech last fall by Defense Secretary Leon Panetta, and some vague language in a 2011 strategy paper, the missions, purpose and scope of conflict have yet to be satisfactorily revealed. One large missing piece is a declaratory policy similar to that used for nuclear weapons in the Cold War, when nuclear policy was openly debated without divulging important secrets. There’s also little public information about rules of engagement for forces or about chain of command and authority to use them. The nature of the threat should also be exposed to a generous dose of sunlight. If conflict in cyberspace is underway, then it is important to sustain support for the resources and decisions to fight it, and that will require more candor.