In the context of U.S. defense policy, “deterrence” is typically understood to mean “nuclear.” And America’s nuclear triad — ground-based missiles, air-delivered bombs, and submarine-launched missiles — serves as America’s biggest form of deterrence, which underwrites everything its men and women in uniform do.

But according to Chief of Naval Operations Adm. John M. Richardson, nuclear weapons are just one of multiple elements of deterrence the U.S. must consider either for itself, or for being aware that other nations might be using them. During a July 2 breakfast presentation hosted by the Mitchell Institute for Aerospace Studies in Washington, Richardson laid out five such elements of deterrence already in use or that must be considered more deeply.

Nuclear

“It’s an incredibly powerful military capability where potentially everybody gets destroyed,” Richardson said. “We must maintain our ability to be competitive and relevant in this domain … [and] strike back at anybody who can pose an existential nuclear threat to the homeland.”

The triad itself includes ground-based missiles — commonly referred to as intercontinental ballistic missiles; submarine-launched ballistic missiles; and air-launched cruise missiles dropped from bomber aircraft. In all three areas the U.S. is underway with modernization efforts.

But the nuclear environment globally is changing, Richardson said.

“More nations are seeking to join the club,” he said. Some of those nations can bring high-tech weapons, while some are using low-tech, including dirty bombs and systems that can be manufactured with 3-D printers. Additionally, not all nuclear weapons are “strategic” in nature. Some are smaller “tactical” weapons.