This idiom is similar to ‘have one’s back against the wall’ in English. It means to be in a bad situation in which one’s ability to act is limited. However, it has an added image into it, which is to cheer ourselves up to get back on our feet. It originated from a Chinese battle story, the Battle of Jingxing or Battle of Tao River which I will discuss in a bit.
背(hai)= It means ‘back’.
水(sui) = It expresses water, but in this context, it implies ‘river’ specifically.
之(no)= It is only a particle.
陣(jin)= It literally means ‘formation’.
During the Battle of Jingxing, a military general named Han Xin marched with his army out of Jingxing Pass and across the Tao River to meet the Zhao forces. Han was defeated and had to withdraw in his position. However, Zhao army was in hot pursuit of the Han forces, making them to ‘have their backs against the wall’. They were left with no choice but to fought ferociously. With the help of their fortifications, they were able to hold out.
If you are interested in these Kanji, you may simply copy them from this website and use them as you please. Make them yours!