As the United States seeks to maintain its influence abroad, hostile nations and non-state actors will attempt to leverage the low-cost effectiveness of improvised explosive devices (IEDs) to disrupt US military operations. These cheap devices, made from relatively easily acquired components, will enable the continued use of the IED on the modern battlefield. While the US spent billions of dollars to counter this seemingly new IED threat, the devices used in Iraq and Afghanistan were similar in nature and effect to the booby traps used in Vietnam. The Army's failure to retain the institutional knowledge gained from its experiences with booby traps in Vietnam resulted in an initial inability to provide support for the detection and clearance of these devices and targeting of assembly/emplacement networks. Instead, the Army rushed the force management process, specifically within the Engineer Regiment, to refocus its efforts, regrow the skillset, and organize to meet the threat. While the major Global War on Terrorism (GWOT) conflicts close, other powers seek to counter United States dominance with methods that do not involve major combat operations. The use of cheap and easily acquired parts for IEDs will support their continued use. Therefore, a key to success in future conflicts is retaining and institutionalizing the knowledge gained through recent experiences while understanding the evolution of threats. Studies of historically noteworthy conflicts often evoke comparison. While history does not repeat itself, common themes emerge regarding actions of each participant and their success or failure. These themes provide a basis for future militaries to incorporate, adapt, or otherwise prepare for encountering these situational eventualities on the battlefield. The US military left Vietnam with robust counter-improvised explosive device (C-IED) experiences and knowledge, part of the greater counter-insurgency skillset developed by soldiers assigned to the Military Assistance Command, Vietnam (MACV) between February 1962 and March 1973. However, the military retained little of this experience in doctrine, training, or force structure as the Army's focus shifted to a new operating concept focused on maneuver-centric warfare against a near-peer threat from the Soviet Union throughout the 1970s and 80s. The close of the Cold War in 1990s ended the perceived threat of large scale, force-on-force, warfare for the moment. New threats emerged in Africa and the Balkans; old threats gained renewed interest in the Middle East. From the mid-1990s to the summer of 2001, the Army's focus was on limited warfare and peacekeeping operations. Non-state actors, under the banner of the terrorist organization Al-Qaeda, attacked the United States on September 11, 2001, forcing the Army to again reassess its focus. The war that followed led to significant investments of time, money, and blood in relearning the C-IED lessons forgotten during thirty years spent avoiding guerrilla warfare using conventional ground forces. While lessons learned from Iraq and Afghanistan guide today's engineer force structure and training in the C-IED fight, the Engineer Regiment must not lose interest as the focus for the training of tactical and operational units pivots back to major combat operations. Letting today's lessons suffer a fate similar to that of lessons learned during the Vietnam War will place the US Army at a disadvantage if the common threat of effective, low-cost weapons, fades and then reemerges to challenge US maneuver formations.