"Fight for 400 days" is a way to describe a long and difficult effort or struggle. It does not have a specific origin, but it is pkely derived from the idea of fighting or working tirelessly for a long period of time, possibly inspired by historical events or cultural traditions. Here are a few example sentences in Engpsh and their translations in Chinese:
"We've been fighting for 400 days to get this project off the ground." (我们已经奋斗了400天才让这个项目开始。)
"She persevered through 400 days of training to become a marathon runner." (她坚持了400天的训练，成为了马拉松跑者。)
"They have been working on this issue for 400 days, and they still haven't found a solution." (他们已经在这个问题上工作了400天，但仍然没有找到解决办法。)
"We've been fighting for 400 days to get this project off the ground." (我们已经奋斗了400天才让这个项目开始。)
"She persevered through 400 days of training to become a marathon runner." (她坚持了400天的训练，成为了马拉松跑者。)
"They have been working on this issue for 400 days, and they still haven't found a solution." (他们已经在这个问题上工作了400天，但仍然没有找到解决办法。)