As this article from the December 1, 1852 edition of the Chicago Daily Tribune relates, Commodore Perry's first expedition to Japan that set sail in 1852 from Norfolk, Virginia planned to include a fleet of over 10 ships and over 880 guns, “mostly of heavy ordnance.” In fact, only four ships entered Japanese waters due to equipment issues and changes en route. It is safe to say that the Americans were prepared for a fight when they pulled into Uraga Bay (now Tokyo Bay) near Edo (Tokyo) on July 8.
The Paixhan shell guns mentioned refer to newly-developed explosive shells. The threat of force was enough to complete the mission: deliver a letter from President Fillmore and prepare to return next year. The President pledged peace and friendship should Japan open its ports to trade after nearly 250 of the reclusive policy of the Tokugawa shogunate, known as sakoku 鎖国 (lit. locked or closed country).