Trump is right. The U.S. should expand its nuclear weapons.

The United States needs a robust nuclear force, therefore, not because anyone wants to fight a nuclear war, but rather, the opposite: to deter potential adversaries from attacking or coercing the United States and its allies with nuclear weapons of their own.

Under President Barack Obama, the United States mindlessly reduced its nuclear arsenal even as other nuclear powers went in the opposite direction, expanding and modernizing their nuclear forces. Such a path was unsustainable and Trump is correct to recognize that America’s aging nuclear arsenal is in need of some long overdue upgrades.

So, what would expanding and strengthening the nuclear arsenal look like?

First, the United States must modernize all three legs of the nuclear triad (submarines; long-range bombers, including a new cruise missile; and intercontinental ballistic missiles, or ICBMs). The Obama administration announced plans to modernize the triad under Republican pressure, but critics are already trying to kill off the ICBM and the cruise missile, and production timelines for these weapon systems keep slipping into the future. The Trump administration must make the timely modernization of all three legs of the triad a top priority.

Second, the United States should increase its deployment of nuclear warheads, consistent with its international obligations.