This monograph examines the changes in the US training of the Afghan National Army (ANA) from 2001 to present. It looks at historical examples of Security Force Assistance from the late 1700s through the 1990s to establish four training concepts to be followed as the ANA becomes a modern and fully developed armed force. The four historical training concepts are the development of small-units, training on small-unit tactics, development of officer training, and training for non-commissioned officers. As technology progressed, two additional concepts were added; literacy and technical training. The ANA training timeline began with US Special Forces conducting the initial training of Afghan soldiers within three months of the September 11 attacks. This was followed by training led by the international community under the Office of Security Cooperation -- Afghanistan, and subsequently, Task Force Phoenix. The most recent iterations of ANA training have seen US Special Forces again training the ANA, but transitioning this task to the General Purpose Forces of the US Army with oversight provided by the NATO Training Mission--Afghanistan due to the finite number of Special Forces soldiers available to train the increasing number of Afghan soldiers that require training. Coalition Forces have recognized that conventional military action alone is not sufficient to ensure the enduring success of the ANA. Success in contemporary military operations will be determined in large part by how well and how quickly the ANA can assume the responsibility for security from the coalition. The goal must be that the ANA is an accountable, self-sustaining, capable and credible force able to meet the security challenges faced by Afghanistan and looked upon as legitimate by the population. Achieving this may take years, but all activities should seek to achieve this aim. Ultimately, this legitimizes Afghan authority and enables the exit of coalition forces.