Editorial: Absent New START, we need a new nuclear arms treaty

When Americans — when any Westerners — find themselves in agreement with the reasonable, nuanced tone of Vladimir V. Putin on a sensitive international issue, you know the world has gone topsy-turvy.

Yet that is the case facing the West this week.

The New START treaty, versions of which have kept the world safe from nuclear catastrophe for generations, expired last Thursday. In the lead-up, the Russian president casually suggested the 15-year-old agreement be informally extended...