The ARVN began as a postcolonial army that was trained by and closely affiliated with the United States and had engaged in conflict since its inception. Several changes occurred throughout its lifetime, initially from a 'blocking-force' to a more modern conventional force using helicopter deployment in combat. During the American intervention, the ARVN was reduced to playing a defensive role with an incomplete modernisation, and transformed again following Vietnamization, it was upgeared, expanded, and reconstructed to fulfill the role of the departing American forces. By 1974, it had become much more effective with foremost counterinsurgency expert and Nixon adviser Robert Thompson noting that Regular Forces were very well-trained and second only to the American and Israeli forces in the Free World and with General Creighton Abrams remarking that 70% of units were on par with the US Army. However, the withdrawal of American forces by Vietnamization meant the armed forces could not effectively fulfill all of the aims of the program and had become completely dependent on U.S. equipment since it was meant to fulfill the departing role of the United States.