I was very excited to be able to see Arlington National Cemetery. More than 4 million people visit each year alone, which is impressive to say the least. When we first arrived we walked up to view the grave site of President John F. Kennedy which sits downhill from the Arlington House. We walked up and took a quick look at the house and admired the views of Washing from there, and then walked back down and around to the Tomb of the Unknowns.
An impeccably uniformed relief commander appears on the plaza to announce the Changing of the Guard. Soon the new sentinel leaves the Quarters and unlocks the bolt of his or her M-14 rifle to signal to the relief commander to start the ceremony. The relief commander walks out to the Tomb and salutes, then faces the spectators and asks them to stand and stay silent during the ceremony.
The relief commander conducts a detailed white-glove inspection of the weapon, checking each part of the rifle once. Then, the relief commander and the relieving sentinel meet the retiring sentinel at the center of the matted path in front of the Tomb. All three salute the Unknowns who have been symbolically given the Medal of Honor. Then the relief commander orders the relieved sentinel, "Pass on your orders." The current sentinel commands, "Post and orders, remain as directed." The newly posted sentinel replies, "Orders acknowledged," and steps into position on the black mat. When the relief commander passes by, the new sentinel begins walking at a cadence of 90 steps per minute.
The Tomb Guard marches 21 steps down the black mat behind the Tomb, turns, faces east for 21 seconds, turns and faces north for 21 seconds, then takes 21 steps down the mat and repeats the process. After the turn, the sentinel executes a sharp "shoulder-arms" movement to place the weapon on the shoulder closest to the visitors to signify that the sentinel stands between the Tomb and any possible threat. Twenty-one was chosen because it symbolizes the highest military honor that can be bestowed -- the 21-gun salute.