What are men to rocks and mountains

The letter

William had been standing behind The Captain dutifully for the past few minutes as they checked out the commotion in the library. Alison and Mike were there, Alison apparently having fallen off a ladder, taking a bookshelf with her. What did surprise him however, was the collection of letters and papers that were laying around the books on the floor. He saw the Captain tensely instruct Alison to throw the letters out as they were revealed to be his. They must have either been top secret or incredibly private for the Captain to have hid them behind the books all those years ago, he'd never ever seen those letters before, and he hadn't known that the Captain would hide documents in the library at all. Some part of him felt a little bit hurt. He and the Captain had always been a team, there was very little that they wouldn't share with each other, especially when it came down to military tactics and strategies. He didn't understand what could have been so disastrous that the Captain felt the need to hide it among a bunch of books in an ancient library?

That was, until Mike had left the Library with a huff, muttering something about cleaning the pond before the sun set, excused himself to nobody in particular, and Alison, who had gathered most of the letters on the Captain's command, brushed past him and accidentally dropped one of the envelope's. It had his name on it. And it had the Captain's handwriting.

William's eyes widened as he automatically bent down to grab it, holding it up for the Captain to see.
"Isn't this your handwriting?" he asked, praying that he was right. It would make for a very uncomfortable situation if he was wrong. The Captain seemed to be having trouble making eye-contact, instead raising his chin and staring straight ahead.
"Mhmyes... It would seem so." He replied shortly. Havers looked back at the sealed letter, its corners bent and even ripped slightly, the paper having begun to deteriorate slightly over the years. He could see the multiple pages of a letter within the envelope, and he was dying to know what it contained.
"It has my name on it... Is it for me, sir?" He asked. No use in beating around the bush. He could see that the question made the Captain incredibly uncomfortable.
"Yes. I planned to write to you in Tunisia, wishing you good luck. But before I could post it- well..." He trailed off. Alison was still standing in between them with the letters in her arms when the Captain turned his attention to her.

"I got a certain letter." He said, gesturing to the pile.
"Third one in your left hand if you please, Alison." Alison shuffled the letters around a bit before dumping all of them on the nearest side-table, except for the one the Captain had asked for of course. It was a small envelope, blank- save for a worn stamp that sat squarely in the middle of it in red ink. It looked incredibly official, almost hauntingly so. Even more haunting was the look on the Captain's face as he saw the letter that had given him the worst news of his entire life. He remembered vividly opening the envelope with shaky hands, already knowing its contents. His worst nightmare had just become a reality, and he had stood frozen for a dozen minutes with the open envelope, not daring to take out the letter inside it. Reading it would make it real. He didn't want it to be real.

"I think you should read that one instead, Havers." The Captain said, gesturing to the one Alison was holding, he couldn't care less if he wasn't being subtle. He needed that letter out of Havers' possession. "I think you'll find it more informative than that silly old letter you have there."
"Yes, I suppose" Havers agreed, lips pursed. But he continued. "I'll read that one first, I can always read this one later."
The Captain stayed silent for a moment, contemplating how he could go about this subtly, when he decided he couldn't and just spat it out.
"No, Havers. I am asking you- not as a Captain, but as a friend- to keep the letters closed. I'm afraid they were very much a product of a time long gone. A time I don't wish to bring up again. I would like to move on from it, in fact. So please... Don't read them."