The Plate Carrier was largely a United States led innovation resulting from the need to house self-contained NIJ level IV threat plates; first SAPI followed by ESAPI plates.
Most United States body armor of the 1980's and '90s consisted of soft armor (NIJ levels IIIa, II, or lower) with additional hard or soft trauma plates to reduce impact force and/or spalling. Other soft armors incorporated heavy steel plates to increase the NIJ threat level; spalling from the steel plates would, in theory, be stopped by the soft armor. Ceramic level IV plates, however, are true standalone armor that requires no additional soft armor as the plates retain all harmful fragmentation. Level IV plates may still be supplemented by soft armor to expand coverage.
While early SAPI carriers like the RBA (Ranger Body Armor) and OTV (Outer Tactival Vest) incorporated standard cut soft armor in addition to SAPI plates, they were cited as being too hot in the middle-eastern theater, were difficult to remove for triage, difficult to use in conjunction with newer load-bearing systems, and not designed to distribute the load from the newer PALS attachment methods that were incorporated more into the later versions of the vests. While there were many steps in the evolution of the modern armor systems of the United States, the ultimate transition was toward the minimal coverage of soft armor in conjunction with hard ESAPI plates focusing on the vital organs of the torso. Additional coverage is instead provided in separate components allotted or sold to soldiers in the forms of groin, thigh, DAPS (Deltoid Auxiliary Protection System), and in various other forms applicable to the armor system being issued.
This transition to plate carries was also seen in other NATO countries around the world and the United States law enforcement and civilian markets. With cheaply available AR500 and similar steel armor in sizes comparable to SAPI/ESAPI plates, the civilian demand for plate carriers grew. As most Berry Amendment compliant gear companies were inundated with military contracts from the Afghanistan and Iraq wars, counterfeit companies, such as condor, flooded the markets to appease the civilian demand for cheap gear. Coincidentally the Asian sport airsoft was also becoming popular in the United States, further increasing the demand for counterfeit gear.
Modern military plate carries usually consist of front and back bags to house ESAPI plates (varying sizes), side plate bags to house side ESAPI plates (6”x8” standard), Level IIIa armor to match the coverage of the ESAPI plates, and usually optional level IIIa shoulder protection. These are usually complimented by a level IIIa helmet, ballistic eye-wear, and possibly level II or IIIa armor inserts for the groin/thigh area to compose an Armor System.