Having set out the tone of his mission, when the Sino-Japanese war ended, he led the way for the combination of European powers which compelled Japan to withdraw her demands for territory amongst her war gains. Immediately after, and against the efforts of the British Government he was instrumental in arranging for the acquisition for Russia of long term concession of Port Arthur and Talien Bay on the Liaotung peninsula, as well as rights to link these by railroad to Russian lines. Recognizing the strategic importance of his role, Cassini is said to have told his niece and adoptive daughter Marguerite that "To possess the East, Russia must possess the Liaotung peninsula."