Between secondary school and his university education, Willem-Alexander performed military service in the Royal Netherlands Navy from August 1985 until January 1987.
He received his training at the Royal Netherlands Naval College and the frigates HNLMS Tromp and HNLMS Abraham Crijnssen, where he was an ensign.
In 1988 he received additional training at the ship HNLMS Van Kinsbergen and became a lieutenant (junior grade) (wachtofficier).

As a reservist for the Royal Netherlands Navy, Willem-Alexander was promoted to Lieutenant Commander in 1995, Commander in 1997, Captain at Sea in 2001, and Commodore in 2005.
As a reservist for the Royal Netherlands Army, he was made a Major (Grenadiers' and Rifles Guard Regiment) in 1995, and was promoted to Lieutenant Colonel in 1997, Colonel in 2001, and Brigadier General in 2005.
As a reservist for the Royal Netherlands Air Force, he was made Squadron Leader in 1995 and promoted to Air Commodore in 2005.
As a reservist for the Royal Marechaussee, he was made Brigadier General in 2005.

Before his investiture as king in 2013, Willem-Alexander was honorably discharged from the armed forces.
The government declared that the head of state cannot be a serving member of the armed forces, since the government itself holds supreme command over the armed forces.
As king, Willem-Alexander may choose to wear a military uniform with royal insignia, but not with his former rank insignia.
Between secondary school and his university education, Willem-Alexander performed military service in the Royal Netherlands Navy from August 1985 until January 1987. He received his training at the Royal Netherlands Naval College and the frigates HNLMS Tromp and HNLMS Abraham Crijnssen, where he was an ensign. In 1988 he received additional training at the ship HNLMS Van Kinsbergen and became a lieutenant (junior grade) (wachtofficier).
As a reservist for the Royal Netherlands Navy, Willem-Alexander was promoted to Lieutenant Commander in 1995, Commander in 1997, Captain at Sea in 2001, and Commodore in 2005. As a reservist for the Royal Netherlands Army, he was made a Major (Grenadiers' and Rifles Guard Regiment) in 1995, and was promoted to Lieutenant Colonel in 1997, Colonel in 2001, and Brigadier General in 2005. As a reservist for the Royal Netherlands Air Force, he was made Squadron Leader in 1995 and promoted to Air Commodore in 2005. As a reservist for the Royal Marechaussee, he was made Brigadier General in 2005.
Before his investiture as king in 2013, Willem-Alexander was honorably discharged from the armed forces. The government declared that the head of state cannot be a serving member of the armed forces, since the government itself holds supreme command over the armed forces. As king, Willem-Alexander may choose to wear a military uniform with royal insignia, but not with his former rank insignia.
Willem-Alexander of the Netherlands