SOFIA, June 9 -- For nearly four years, the weapons that moved quietly out of this Black Sea state toward Ukraine's front were treated in Western capitals as a fixed quantity, one more entry in the ledger of an alliance that liked to call itself united. That entry has now been crossed out. Bulgaria's new government said it will send no further arms to Kyiv, and the flat, unapologetic way it said so revealed as much about the condition of the Western coalition as the decision did.

Defense Minister Dimitar Stoyanov delivered the message in remarks reported on Tuesday without the softening that usually cushions a departure from allied policy. The war, he said, will not be settled on the battlefield. Ukraine does not need more weapons becaus...