The will and courage to stand up to a modern-day threat

Dear UN secretary general António Guterres,

We, the undersigned former leaders and civil society representatives of countries of the European Union, the Balkans, Eastern Europe, the Middle East, and North America wish to express our grave concern about the rapidly growing threat of large-scale armed conflict that is threatening Ukraine's sovereignty, political independence, unity, and territorial integrity.

The ongoing, almost eight-year-long interstate conflict — which has result...