Ukraine Wants to Join the E.U. to Secure Peace. Here’s What to Know.

Negotiators agree that joining the bloc is critical to Kyiv’s future. But obstacles abound, and compromises might forever change how the union works.From left, António Costa, president of the European Council; President Volodymyr Zelensky of Ukraine; and Ursula von der Leyen, president of the European Commission, in Brussels last year.