Every year, Memorial Day marks the unofficial beginning of the summer season. Grills are brought out from storage, hot dogs and hamburgers are served up with potato salad and pickles with ice cream for dessert. But, traditionally, the last weekend in May every year also serves as a reminder for our country of the sacrifices of those who have fought and died in her honor.

Since 1863, when grieving mothers, wives, daughters, sisters, and other loved ones cleaned confederate soldiers’ graves in Columbus, Mississippi, placing flowers on them even as the Civil War raged on, our Nation has honored and remembered those who gave their lives to the most noble of causes … Freedom.

Today, 145 years later, we are once again approaching Memorial Day. And, we are once again at war, fighting the Global War on Terror, and honoring those we have lost. Grieving family members and friends, and untold others, will visit Arlington National Cemetery and other cemeteries around the country to pay tribute to the fallen, past and present.

Indeed, in the nearly seven years since the attacks of September 11, 2001, more than 4,000 members of our armed forces have died protecting our liberty during this war. As of this writing, 529 of them are citizen-Soldiers and –Airmen.

On this Memorial Day, my thoughts will be sharply focused on these 529 heroes, their families, friends, comrades and their country. My thoughts will also be on those who mourn their tragic losses in hopes that they may soon heal and find joy and strength in the memory of these Soldiers and Airmen.

These 529 brave men and women represent a National Guard that serves our Nation from every ZIP Code. They are the epitome of what I mean when I say, “If we didn’t have a National Guard we would have to invent one.” They embody the idea, “When you call out the Guard, you call out America.”

These men and women hailed from nearly every state and territory in our nation … places like Mineral Bluff, Georgia, Bozeman, Montana, Nashua, New Hampshire, and Barrigada, Guam.

They left their families, friends and jobs behind in order to serve a purpose higher than their own.

At war they may have been infantrymen, mechanics, convoy drivers and medics. At home they may have been policemen, lawyers, paramedics and school teachers. But, they were also the sons and daughters, family members and friends of those they left behind. Today, they are American heroes.

But, let there be no doubt: all of them were American heroes before they gave their lives because each of them volunteered to serve this country knowing the risk of such selflessness.

It’s important to remember that this is the first protracted war our Nation has fought with the post-Vietnam, all-volunteer military, and our Nation owes a debt of gratitude to all of those who choose to serve.

Service in our National Guard goes far beyond fighting wars overseas. Each and every day, an average of 17 Governors call on their National Guards for everything from weather related assistance to suspected anthrax contamination.  These Soldiers and Airmen, many veterans of more than one deployment into combat areas, risk their lives here at home for their fellow citizens, doing things like conducting search and rescue operations in the mountains of Alaska; recovery operations following a major weather disaster like the Greensburg, KS, tornado that wiped a whole town off the map; hauling water to drought stricken portions of Tennessee. The list really does go on.

And, unfortunately, there is sacrifice associated with these domestic missions as well. A Mississippi National Guard Soldier lost his life immediately following hurricane Katrina. He was on a rescue operation trying to save his neighbors in the aftermath of one of the most powerful of nature’s furies. And, not unlike the call to arms when fighting a war, the National Guard responded to this domestic crisis, saving more than 17,000 lives and relocating more than 70,000 people in that storm’s aftermath. More than 50,000 Soldiers and Airmen from every state and territory responded to the Gulf Coast region.

These brave Soldiers and Airmen, whether fighting overseas or serving here at home, are strong examples for all those who follow in their footsteps, as they have followed in footsteps 372 years in the making.

On this Memorial Day, I hope each of you will stop for a moment and think about how wonderful it is to live in this great Nation. I hope you will think for a moment about the freedoms you enjoy. I hope your thoughts, like mine, will turn to all those who have died protecting our freedom, and those they left behind.

Lastly, on this Memorial Day, indeed every day, please take the time to think about the 529 citizen-Soldiers and –Airmen who have given their lives during this long war on terror. They are part of your National Guard with a proud history and tradition of being always ready, always there.

Blum is chief of the National Guard Bureau.