During the days when India was controlled by The British Empire, the IPS dealt with the political affairs of The Raj. Specifically it provided liasons to semi-independent principalities and conducted policy with various tribes in the border regions. In other words it did much the same kinds of jobs that the CIA and the US Army Special Forces often do in Afghanistan today.
Another part of it's mission was scouting in Central Asia. At this time the area was unexplored and Britain and Russia, competing for influence in this area would send agents as explorer/spies(historically the combination was actually fairly common). This competition became known as The Great Game. At first the British had no official organized espionage system but that changed as time went on and many of Britain's best spies came from the IPS.
During the Russian Civil War the Great Game took a new form with an element of ideology added to it. The British were unsure of their policy at the time and desperate to get any intelligence possible. IPS agents entered into the chaos to see what was going on. There were a number of interesting events including one British agent who was recruited by the Bolshivik Secret Police to hunt himself down.
After the dissolution of The British Empire, the IPS as such also lapsed. However difficulties in the area have in many ways remained the same, and much of the work done by modern intelligence agents in the area, would be recognized by the IPS.
IPS In Fiction:
- Kim by Rudyard Kipling . One of the most famous espionage novels in history. While the IPS is not mentioned by name, the title character does much of the sort of thing that the IPS actually did.
- Flashman works as a political while in India in a couple of books.
- In Traveller the IISS is something like the IPS Recycled In Space; at the least it undertakes the same sort of missions and has a similar elan.
- Peter Hopkirk's The Great Game series.