AP Photo

We hope that we will very soon have reason to welcome a new agreement between the United States and Russia on further reductions of strategic nuclear weapons. It makes no sense for either country to spend billions on weapons systems of such radically diminishing strategic utility.

But as we look forward toward welcoming such an agreement, we simultaneously call for early progress on steep reductions in substrategic nuclear weapons — in Europe often referred to as tactical weapons.

While strategic nuclear weapons are seen as a mutual threat by the United States and Russia, nations like Sweden and Poland could have stronger reason to be concerned with the large number of these tactical nuclear weapons.

Most of the active substrategic nuclear weapons in the world...