Nobori banners, carps, warrior's Yoroi and Kabuto helmets, samurai dolls and swords were all a part of the display used for Boy's Day (renamed Children's Day) on May 5th in Japan. They reflect the parents' wish to inspire their sons in manliness, discipline, bravery and the honor codes which are associated with them.
Originally, nobori were used on the battlefield to identify the troops; some were to show the warriors where their taisho (general) was, others were used to shift the troops. It took several men to hold the big Nobori banners. It was an effective tool in the 16th century especially when numbers exceeded 100,000 in major battles. Drums and trumpets were also used for the same reason.
When Ieyasu (Tokugawa) took control and united Japan at the beginning of the Edo period (1603-1868), it was the end of major battles. Nobori banners became more ornamental rather than tools for battle. The families of samurai started to display nobori along with their armor to celebrate the birth of their boys and probably for other ceremonial occasions. When this custom started to spread to the general population in the mid Edo period, koi-nobori (banner in the shape of a carp), streamers and ornamental banners were created. They were made out of paper because cotton was still a very expensive commodity. The sky was filled with them for the Sekku (Boy's Day in May) in the late Edo period and must have been one unforgettable sight. Unfortunately, paper made koi-nobori from mid to late Edo period did not survive to today.
Just washed before the photos were taken. The cotton is loosely woven; there is a small L shaped tear close to the edge of the bottom area. The family crest at the top is a popular "mokko", melon or cucumber (sliced side) crest. ODA Nobunaga had the similar crest. The dimensions: 28 1/2"W x 198 1/2" (16' 6 1/2")L. The length of main design is 143 1/2" long from the bottom. Circa 1930-1940.