The first attack occurs on June 25, 1863, soon after the Imperial "Order to expel barbarians" comes into effect.

The U.S. merchant steamer SS Pembroke, under Captain Simon Cooper, is riding at anchor outside Shimonoseki Strait when intercepted and fired upon by two European-built warships belonging to the rebel forces.

The crew of one enemy vessel taunts the frantic American seamen with a loud and unnerving cry: "Revere the Emperor and expel the barbarians!" (sonnō jōi).

Under incessant cannon fire, Pembroke manages to get underway and escape through the adjacent Bungo Strait with only slight damage and no casualties.