New Delhi, June 6 -- KYIV - The drones flew roughly 1,000 kilometres through the night, and when they arrived over Kronstadt, the Russian Baltic Fleet's historic island base west of St. Petersburg, they found their mark. A guided-missile corvette, the Boikiy, caught fire in dry dock. Smoke from the Kronstadt Marine Plant rose in thick columns visible from the city where Vladimir Putin was, at that moment, hosting the final day of his signature economic forum.

Ukraine's military carried out one of its deepest large-scale drone strikes of the conflict overnight on June 6, targeting naval arsenals, energy infrastructure and weapons manufacturing sites stretching from the Black Sea coast to the outskirts of St. Petersburg. President Volodymy...