William Arkin:

For the first time since intercontinental ballistic missiles were "captured" in arms control treaties 40 years ago as unique and potentially destabilizing weapons, the United States will muddy the waters by modifying an existing nuclear weapon for use in day-to-day warfare.

The conversion of Trident missiles abandons the strict segregation of nuclear from conventional weapons.

Were the United States ever to use its new conventional Tridents, the firing would also flirt with accidental nuclear war. Ballistic missiles aimed at targets in North Korea, for example, might falsely signal to China or Russia that the United States was attacking them.