15th Cavalry Regiment ( United States ) The 15th Cavalry Regiment is a cavalry regiment of the United States Army . It was one of the Expansion Units originally established for the Spanish – American War , but has been a general workhorse unit ever since . History . Origins . The 15th Cavalry Regiment was formed in 1901 at the Presidio of San Francisco , California . Immediately upon its organization in 1901 , the 15th Cavalry embarked for the Philippines to quell an insurrection in the United States ' newly acquired territory . The fierce combat in the Philippine jungles against the savage Moros forged the spirit of the Regiment in fire and blood ; a spirit exemplified in the motto the Regiment chose for itself - TOUS POUR UN , UN POUR TOUS ( All for one , one for all ) . The Regiment ' s next action was part of the Cuban Pacification from 1906 to 1909 , followed by duty along the Mexican border and the hunt for Pancho Villa from December 1917 to March 1918 . World War One . When the United States entered World War I , the Regiment sailed for France as one of the four mounted Regiments on duty with the Allied Expeditionary Force . The fighting had already bogged down into trench warfare and the role of horse Cavalry was nearly over . The 15th was called upon to dismount and relieve exhausted infantry units in the trenches . It was the tank that finally broke the trench lines to end both the war and the role of the horse soldier . The 15th served occupation duty after the war until June 1919 when it returned to the United States . Sadly after 20 years of continuous active service , the Regiment was deactivated on 18 October 1921 as part of the massive cutbacks in the Regular Army following the " war to end all wars " . World War Two . With the advent of the Second World War , the 15th was again called to service in March 1942 . The spirit and elan of the Cavalry were to lead the Army again , this time with new mounts , the armored car and tank . After undergoing training at the Desert Training Center in California , the regiment sailed for the European Theater of Operations , arriving in Scotland in March 1944 . Here , the 15th was reorganized as the 15th Cavalry Group ( Mechanized ) . The Group was composed of the 15th and 17th Reconnaissance Squadrons . The 15th Cavalry Group landed on Utah Beach on the 5 July 1944 as part of Patton ' s Third Army . The 15th served in four major campaigns in Europe : Normandy , Northern France , Rhineland , and Central Europe . The 15th Cavalry Group and its two squadrons fought as part of the Third Army , Ninth Army and was later assigned as a security force for several different divisions . The end of the war found the 15th deep inside Germany , covering over 1000 miles of enemy held territory since landing on the Continent began in June 1944 . When the war ended , the 15th Cavalry Group and its two squadrons had taken nearly 7000 German prisoners and had destroyed 78 guns and 495 enemy vehicles . Postwar - the Constabulary Era . Following the war , the 15th was redesignated the 15th Constabulary Regiment , charged initially with occupation duty of the defeated Germany . The 17th Reconnaissance Squadron was deactivated in January 1947 , but the 15th Squadron , redesignated as the 15th Constabulary Squadron , continued serving . As the cold war began in earnest , the Regiment ' s duty shifted to patrolling the border between West Germany and East Germany , as well as the border with Czechoslovakia . The Constabulary Force guarded the border until 1952 . Service during the Cold War . From 1952 to 1987 , the Regiment went through a series of redesignations , inactivations and reactivations . Elements of the regiment served across the Army from Korea , Germany , and the United States . Troop G served in Viet Nam from 1971 to 1972 , being equipped at the time with M551 " Sheridan " Armored Airborne Reconnaissance Assault Vehicle ( AARAV ) . Reorganization and current status . In March 1987 , the Army overhauled its Combat Arms Regimental System ( CARS ) to restore some order to the history and lineage of its regiments . One goal of this reform was to keep on active duty those regiments which had earned distinguished records over long years of service . The 15th Cavalry clearly deserved such recognition and in March 1987 , the 15th Cavalry Regiment was reactivated at Fort Knox , Kentucky , by the activation of its 5th Squadron . The Squadron , as part of the 194th Armored Training Brigade , was charged with the mission of training the U . S . Army ' s MOS 19D enlisted Cavalry Scouts . Portions of the 17th ' s movements are dramatized in the book , " Teacher of the Year : The Mystery and Legacy of Edwin Barlow " . ( Inactivated October 1921 , reactivated March 1942 ) ( Redesignated March 1944 as 15th Cavalry Group , Mechanized ) ( Redesignated May 1946 as 15th Constabulary Regiment ) ( Inactivated December 1948 , reactivated November 1950 as 15th Armored Cavalry Group , Mechanized ) ( Redesignated September 1953 as 15th Armor Group ) ( 15th Armor Group Inactivated December 1955 , incorporated into the Combat Arms Regimental System 1957 , regimental headquarters disbanded . )