In 1968, Cavalier Aircraft owner/founder David Lindsay began developing a highly modified version of the Cavalier Mustang for use as a counter-insurgency aircraft. Cavalier initially mated a Rolls-Royce Dart 510 turboprop to a Mustang II airframe. This privately funded prototype was also intended for the same CAS/COIN mission that the Mustang II was built for. The Turbo Mustang III had radically increased performance, along with an associated increase in payload and decrease in cost of maintenance, and was equipped with Bristol ceramic armor to protect the engine, airframe and pilot. Despite numerous sales attempts to the United States Air Force, neither the U.S. military nor any foreign operators purchased the Turbo Mustang III.
Seeking a company with mass production capability, the Turbo Mustang III, renamed the "Enforcer," was sold to Piper Aircraft in late 1970. Cavalier Aircraft Corp. was closed in 1971 so the founder/owner, David Lindsay, could help continue develop the Enforcer concept with Piper. Piper was able to lease a Lycoming T-55L-9 engine from the USAF (the engine Lindsay wanted initially) and flew the aircraft some 200+ hours. In 1984 with a $US12 million appropriation from Congress, Piper built two new Enforcers, giving the new prototypes the designation PA-48. These aircraft were evaluated by the USAF, but flown only by Piper test pilots.
In 1971, Piper built two Enforcers by heavily modifying two existing Mustang airframes, fitting them with Lycoming YT55-L-9A turboprop engines along with numerous other significant modifications. One airframe was a single seat (called the PE-1 and FAA registered as N201PE), the other a dual-control aircraft (the PE-2, registered N202PE). Prior to the Pave COIN evaluation, N202PE was lost in a crash off the Florida coast on 12 July 1971 due to flutter caused by a Piper-modified elevator trim tab. Although the Enforcer performed well in the 1971–1972 Pave COIN test flown by USAF pilots, Piper failed to secure a USAF contract.