What is the "sun-piercing steel plate" that World War II people often talk about?

"Sun wears steel plate" is an Internet buzzword, originating from a story in Japan during World War II. At that time, a ship of the Japanese army was trapped in the ice sea. In order to prevent the ship from being crushed by the ice, the Japanese army decided to scuttle the ship. When the ship was scuttled, the Japanese army discovered that there was a three-centimetre-thick steel plate on the bottom of the ship. The steel plate was pierced, but there was still a layer of cork on the bottom of the ship. After the cork was pierced, seawater began to flow into the ship, eventually causing the ship to sink.

This story was later extended by netizens as "Sun Wearing Steel Plate", which is used to describe some things that seem difficult and impossible, but are successfully completed by some people through hard work and firm belief. .