Why did the united states attack okinawa ?

The Battle of Okinawa was one of the bloodiest and costliest of World War II in the Pacific. The United States needed a base to stage an invasion of mainland Japan. The island of Okinawa was the crucial final stepping stone for the Americans. For the Japanese, it would be the first time they met the enemy on home soil.

Explanation:

the perimeter of a triangle is 69 cm. side a is 5 cm shorter than side b. side c is twice as long as side a. find the length of each side. i need to know how to do it in 2 equations.  

equations:

a = b-5

c = 2a

a + b + c = 69

the treaty of brest-litovsk was a peace treaty signed on 3 march 1918 between the new bolshevik government of russia and the central powers (german empire, austria-hungary, bulgaria, and the ottoman empire), that ended russia's participation in world war i.