In japan's Sengoku period, there was an elite unit, which was all equipped in red and was called the "Akabei" team. Because the red paint in Japan at that time had to be made of valuable tatsu sand, it cost a lot of money to equip such a unit. In this way, only the most elite troops will be organized into "red reserves".
Under many daimyōs, they were organized into the "Red Reserve". One of the more famous is the Takeda Shingen family's Akabi team. This unit gave the Takeda family a lot of military achievements. In the famous Battle of Mikatahara, Takeda's Akabi defeated the combined forces of the Tokugawa and Oda armies and pursued them directly to Tokugawa Ieyasu's castle.
However, in the later Battle of Nagashino, although the Takeda family's Akabi team fought bloodily until the Oda family's main line, it was eventually defeated by the Oda family's iron cannon, and most of the Akabei team, including the main general Yamagata Masakei, was killed. However, the combat effectiveness of the Akabi team impressed both Oda Nobunaga and Tokugawa Ieyasu.
When the Takeda family collapsed, Oda Nobunaga issued an order not to take in the old subjects of the Takeda family. However, Tokugawa Ieyasu ignored this order and secretly took in many of Takeda's courtiers. These courtiers were very impressed and decided to serve Tokugawa Ieyasu. As a result, Tokugawa also followed the takeda family and formed his own Akabi team, led by I Nobuomasa.
By the time of the Wanli Korean War, takeda Akabei, who had long since perished, could not have appeared on the Korean battlefield. Moreover, Toyotomi Hideyoshi misjudged the situation and had selfish intentions to divide the territory of Korea that he had conquered among his concubines. Therefore, Tokugawa Ieyasu was not allowed to participate in the Conquest of Korea. As a result, the Akabei of the Tokugawa family, which inherited the Takeda Akabetsu, was not able to come to Korea and fight the Chinese army.
If it is really based on strength, Japan's red reserve team is not at all the opponent of Li Rusong's Liaodong Iron Horse. Japanese people and horses are very small, and the Ming Dynasty people at that time ridiculed the Japanese as monkeys riding donkeys, which shows how effective their cavalry is. The Liaodong Iron Horse was Li Rusong's private soldier, with good treatment and high physical fitness. Horses and weapons are selected. General weapons have three-eyed rifles, which can be fired three times in a row and then used for hand-to-hand combat.
The Japanese suffered heavy losses when fighting Li Rusong's cavalry. In the Battle of Biheguan, facing ten times the enemy, Li Rusong's cavalry forced back the Japanese army. From then on, the Japanese army never fought in the field with the Chinese cavalry again.
Therefore, even if the Japanese Red Guards came to the Korean battlefield, they were not the opponents of Li Rusong's Liaodong Iron Horse.