Well, this is definitely unique. I have never seen a Warriors story set during the war.

Story problems-

First of all, it seems doubtful that cats would know much about human politics and warfare. Why did Sky want to break the cable? Why would he care about helping the humans?

Secondly, cats do not live past twenty years of age. The Berlin Wall was built in 1961, and it came down in 1989. 28 years. So, Stripe must be telling the story second-hand as he could not have possibly been alive at the same time as Sky and Earthen. You should insert a page break or a line between the actual story and Stripe telling the story. It would separate the two time periods so that readers are not confused.

-Technical issues

You use too many exclamation points in your dialogue. the majority of your dialogue should end in periods, with exclamation points used only rarely. Also, this:

["Let him up Talon" Sky meowed calmly.]

should be ["Let him up, Talon," Sky mewed calmly.]

You need either a period or a comma before the last quotation mark. When one character calls another by name, there should be a comma before the name. for example: ["Hello, Sky,"] or ["Where are you going, Sky?"]

This is also wrong:

[ "He wants you to meet him in the tunnel now to discuss on finding a new meeting place". ]

...because the period should come before the last quotation mark [."]

Ummm what happened? Why was the Berlin Wall torn down wayyyyyy to early