The WP was created after the Second World War as the standard express locomotive of the Indian Railways. These Pacifics stood out because of their streamlining on the smokebox and were designed to be able to pull heavy trains at up to 120 km/h, even with low-calorie coal. Compared to the similarly powerful pre-war XC, they were a little heavier, but had a lower maximum axle load due to a different weight distribution.

They were initially faster than the existing diesel locomotives and pulled the most important express trains. Between 1947 and 1967, 755 locomotives were built, more than half of which came from North America. Others were made in Poland and Austria. It wasn't until 1963 that 259 were built in India, which were around five tons heavier. Most remained in service into the 1980s and some even survived into the 1990s.