They served their country and the missing records are not their fault, they shouldn’t have to “prove” anything….
Check this out:

Stanley Friedman was shot at. The ship he was on was attacked by enemy bombers. He saw a landmine blow apart a truck carrying two dozen of his fellow soldiers. One of them died in his arms.

But after he came home from World War II, he found himself embroiled in another battle — this time, with the Veterans Administration, as he tried to get his benefits.

In the decades that followed the war, Friedman suffered from anxiety, depression and nightmares which lasted his entire life, affecting his job and his family.