I want to know the answer to the following question:
What were the Leyte beachheads of the U.S. Sixth Army secured from?
All the background I'm provided with is that "The battle secured the beachheads of the U.S. Sixth Army on Leyte against attack from the sea, broke the back of Japanese naval power and opened the way for an advance to the Ryukyu Islands in 1945.". Is that enough to answer the question?