Readers discuss whether military defense and deterrence or diplomacy is most effective.

To the Editor:

In the last few months, North Korea has tested a more powerful nuclear weapon and a three-stage rocket that could reach targets on the West Coast. As the country works to combine these technologies into a long-range nuclear intercontinental ballistic missile, the United States should be taking concrete steps to better protect its citizens.

Our most important protection against Pyongyang’s bomb is the Ground-Based Midcourse Defense missile defense network. Interceptors in Alaska and California have proved they can stop an incoming ICBM with eight successful test kills, leading the White House to declare that we are now “capable of defending against any North Korean ballistic missile attack.” But we must continue to improve radars and expand our interceptor fleet to handle larger-scale raid attacks.

Missile defense has broad bipartisan support; President Obama praised the system in his State of the Union address, and Congress has voted to study expanding it to the East Coast, which was recently recommended by the National Academies of Science. But missile defense doesn’t need cheerleaders; it needs funding.

The administration’s proposal to cut our total nuclear forces in hopes of persuading other nations to do the same is a bad idea. Nothing is going to persuade North Korea to give up its hard-earned nukes, nor can we prevent it from transferring nuclear weapons technology to Iran. We need a strong deterrent to convince Kim Jong-un, the leader of North Korea, that there’s no upside to attack and to assure our allies that they need not seek out nuclear weapons of their own. We can’t stop Kim Jong-un from building a nuclear bomb; let’s not give up the tools to stop him from using one.