According to military author Bryan Perrett, the T-62 never enjoyed the commercial success of the T-54/T-55 series for numerous reasons. First, the T-62 was more than twice the price of the T-55, and many Warsaw Pact nations passed on the new tank because they did not feel that the improvements inherent in it warranted the cost. Secondly, in 1968, a 100 mm HVAPDS tank shell capable of piercing Western armour was developed. Use of this shell made the T-55 gun almost as effective as the T-62s, undercutting the T-62's original selling point: a bigger, more powerful gun. Third, the T-62 was, according to Perrett, almost immediately surpassed on its introduction by the new Western MBTs, the Chieftain and M60. Finally, the T-62 could not keep up with the new Soviet BMP-1 – the principal infantry fighting vehicle that the T-62 was supposed to accompany. All of these factors combined to ensure that long-term investment in the T-62 was not viable and a new Soviet MBT had to be developed.