The Black Ships– kurofune were the shock ‘n’ awe American vessels of Commodore Perry that arrived near Yokohama on July 14, 1853, opening previously closed Japan to trade, and striking fear in the Japanese hearts as shown in the imagery above and in the complex poem written about the day (Wiki).
break the halcyon slumber
of the Pacific;
a mere four boats are enough
to make us lose sleep at night.
Today, September 2nd is Loser Day in Japan aka the surrender of Japan bringing officially ending World War II. However, the day could be the real “Black Ships Day” for Japan as you note in the photo on the right of MacArthur at surrender ceremony that shows the flag flown by Perry is visible in the background.