There is, of course, no such thing as the military perspective -- no single person can speak for all the men and women who have served in the military -- but if you are looking for a military perspective, my first choice would be Lt. Col. Robert Bateman who writes eloquently and intelligently on the subject for Esquire. Here are Bateman's recent thoughts on Memorial Day.
When the guns fell silent in the Spring of 1865, they all went home. They scattered across the country, back across the devastated south and the invigorated north. Then they made love to their wives, played with their children, found new jobs or stepped back into their old ones, and in general they tried to get on with their lives. These men were no longer soldiers; they were now veterans of the Civil War, never to wear the uniform again. But before long they started noticing that things were not as they had been before.
Now, they had memories of things that they could not erase. There were the friends who were no longer there, or who were hobbling through town on one or two pegs, or who had a sleeve pinned up on their chest. There were the nights that they could not shake the feeling that something really bad was about to happen. And, aside from those who had seen what they had seen and lived that life, they came to realize that they did not have a lot of people to talk to about these things. Those who had been at home, men and women, just did not "get it." A basic tale about life in camp would need a lot of explanation, so it was frustrating even to talk. Terminology like "what is a picket line" and "what do you mean oblique order?" and a million other elements, got in the way. These were the details of a life they had lived for years but which was now suddenly so complex that they never could get the story across to those who had not been there. Many felt they just could not explain about what had happened, to them, to their friends, to the nation.
So they started to congregate. First in little groups, then in statewide assemblies, and finally in national organizations that themselves took on a life of their own.
The Mid-1860s are a key period in American history not just because of the War of Rebellion, but also because this period saw the rise of "social organizations." Fraternities, for example, exploded in the post-war period. My own, Pi Kappa Alpha, was formed partially by veterans of the Confederacy, Lee's men (yes, I know, irony alert). Many other non-academic "fraternal" organizations got their start around the same time. By the late 1860s in the north and south there was a desire to commemorate. Not to celebrate, gloat or pine, but to remember.
Individually, at different times and in different ways, these nascent veterans groups started to create days to stop and reflect. These days were not set aside to mull on a cause -- though that did happen -- but their primary purpose was to think on the sacrifices and remember those lost. Over time, as different states incorporated these ideas into statewide holidays, a sort of critical legislative mass was achieved. "Decoration Day" was born, and for a long time that was enough. The date selected was, quite deliberately, a day upon which absolutely nothing of major significance had occurred during the entire war. Nobody in the north or south could try to change it to make it a victory day. It was a day for remembering the dead through decorating their graves, and the memorials started sprouting up in every small town in the nation. You still see them today, north and south, in small towns and villages like my own home of Chagrin Falls -- granite placed there so that the nation, and their homes, should not forget the sacrifices of the men who went away on behalf of the country and never came back.