Kevin would make the point, as a veteran himself, that Memorial Day is not the day to say to veterans "Thank you for your service" (that's Veterans Day) it's the day to remember the honored dead, who didn't live to be thanked. [“Happy Memorial Day?” | WeaponsMan, May 30, 2016]
This year, I want to repeat something I said in 2010, when Obama was President: Memorial Day came into being after the Civil War, as "Decoration Day", a day for memorializing the honored dead, of whom there were a great many, by decorating their graves with flowers.
Because America remained divided, there were actually two Memorial Days celebrated—many parts of the South still proclaim "Confederate Memorial Day" on a different date. The women of Columbus, Mississippi famously decorated the graves of soldiers on both sides in April of 1866, giving rise to a celebrated poem by Francis Miles Finch:
No more shall the war cry sever,
Or the winding rivers be red;
They banish our anger forever
When they laurel the graves of our dead!
Under the sod and the dew,
Waiting the judgment-day;
Love and tears for the Blue,
Tears and love for the Gray.
There have been enough foreign wars since then that Northern and Southern bodies are found in military cemeteries in about equal measure. That North and South were fighting external enemies together was part of the Great Reconciliation that is described in Paul H. Buck's 1937 book, The Road To Reunion 1865-1900, which you can download for free from Archive.org. (This book is now unpopular—and so is the actual post-Civil War reconciliation.)
As part of the reconciliation, Congress in 1878 passed the Posse Comitatus Act, which forbids, roughly speaking and subject to certain exceptions, using American soldiers on American citizens. It was Congress's way of saying "Sorry!" for Reconstruction and the Force Bills, and promising not to do it again.
In 2018, we have a President who recently ordered the National Guard to guard the US/Mexico border. You will occasionally hear that it would be "illegal" to use the actual Army to guard the border because of the Posse Comitatus Act, but this is stupid: the Posse Comitatus Act is about not using troops on Americans--guarding borders is what armies are for.
I mention all this, because of meme popular around 2006 (when Bush was President) which was that America's war dead "didn't die for open borders".
You don't honor the men who died for their country by surrendering it to invaders.
Previous Memorial Day Columns