The Grumman F-111B was the product of the misguided mind of the Secretary of Defense Robert Strange McNamara in his attempts to streamline military procurement. It was too big and too heavy and was shoved down the Navy's throat as a spin-off of the Air Forces General Dynamics F-111. In the end it failed. It however provided a great service as a development airframe for the Phoenix Missile System and gave Grumman the expertise needed to produce the superlative swing wing F-14 Tomcat which remained in use for almost 40 years.