On Jan. 31, U.S. Marine Sgt. William Stacey was traveling through the Helmand province in the southern part of Afghanistan -- his fourth deployment to the country -- when suddenly, a homemade bomb exploded, killing the 23-year-old from Redding, Calif. Stacey had been prepared for this kind of tragedy, having already written a letter to his family that would be opened in the event of his death, which explained why he fought.

On Monday, Marine Gen. John Allen, the top U.S. commander and leader of the NATO coalition currently in Afghanistan, read Stacey's heartrendering letter aloud during a Memorial Day service in Kabul. He read it to honor Stacey's memory, as well as all of those who died in Afghanistan since the war started back in 2001.

Today we remember his life and his words, for they speak resoundingly and timelessly for our fallen brothers and sisters in arms, Allen said.

Here is the full text from Stacey's letter, courtesy of the Seattle Times.

My death did not change the world; it may be tough for you to justify its meaning at all, Allen wrote. But there is a greater meaning to it. Perhaps I did not change the world. Perhaps there is still injustice in the world. But there will be a child who will live because men left the security they enjoyed in their home country to come to his. And this child will learn in the new schools that have been built. He will walk his streets not worried about whether or not his leader's henchmen are going to come and kidnap him. He will grow into a fine man who will pursue every opportunity his heart could desire. He will have the gift of freedom, which I have enjoyed for so long. If my life buys the safety of a child who will one day change this world, then I know that it was all worth it.

Semper Fidelis means always faithful. Always faithful to God, Country and Corps. Always faithful to the principles and beliefs that guided me into the service. And on that day in October when I placed my hand on a bible and swore to defend the constitution of the United States against all enemies foreign and domestic, I meant it.

Stacey, who was deployed to Afghanistan with the 2nd Battalion, 4th Marines, 1st Marine Division out of Camp Pendleton, Calif., is among the 1,851 estimated U.S. military personnel who have died in Afghanistan since the U.S.-led invasion began in 2001. Gen. Allen added that since he took over command of Afghanistan's operations in July 2011, roughly 251 troops, 76 NATO coalition members and 1,296 members of the Afghan security forces have been killed in Afghanistan.

On Monday, three more members of the NATO coalition were killed -- two in a helicopter crash, and one in an insurgent attack.

Mirroring a similar ceremony being performed by President Obama at Arlington's Tomb of the Unknowns, Allen laid a large wreath at the base of a pedestal holding a battlefield cross, which is the symbolic memorial given to all fallen soldiers, erected using the soldier's helmet, boots, rifle, and dog tags. Taps played over a speaker as Gen. Allen saluted.

Even though soldiers continue to die in Afghanistan, support on the war has given way as more countries are ready to pull their troops out and let the Afghan security forces largely fend for themselves. The cost of the war, including the physical cost and the mounting number of casualties, has helped drive U.S. plans to transfer security responsibilities to the Afghan forces by mid-2013. President Obama hopes to have withdrawn most U.S. combat troops from the country by the end of 2014.

Even though many countries are looking to withdraw the troops, Gen. Allen's message to troops on this Memorial Day was to keep fighting. Those who died will not die in vain.

While our brothers and sisters fell in a place far from home, far from their families, the values for which they stood and for which they lived and for which they died occupy an enduring place in our hearts, Gen. Allen said. Those values: freedom, duty, selflessness and sacrifice.