After World War Two the opening became a mainstay in GM competition. Hans Kmoch in Pawn Power in Chess calls the King's Indian configuration of black pawns on c6 and d6 (especially if the d-pawn is on a semi-open file) "the Boleslavsky Wall". Besides the K-Indian, the Boleslavsky Wall can also arise from other openings such as the English, Pirc and even the Ruy Lopez.
The reason the opening was viewed with suspicion was because it was believed that if black had to exchange ...exd4 his Pawn on d6 was left weak. What Boleslavsky proved was that black has a lot of tactical resources available in these types of positions. Of course Boleslavsky wasn't the first to recognize that fact. Just check out the remarkably modern-looking game Paulsen vs Anderssen, Leipzig 1877!
When Boleslavsky (and the others, especially Bronstein) studied this P-formation back in the 1950s they used some the ideas found in the Paulsen - Anderssen game and added some ideas of their own.
White can try:
1) exploitation of d6
2) Pawn breaks e4-e5 or c4-c5
3) Attacking on the Q-side with b2-b4-b5.
Black can try:
1) Q-side play with a7-a5-a4.
2) pressure against white's e-Pawn
3) using the black squares on the a1-h8 diagonal
4) ...h5, ...Kg7 and ...h5 creating mating threats
5) Pawn breaks ...d6-d5 and/or ...f7-f5
Generally speaking, black should avoid the strategy of advancing ...c7-c5 as he did in the previous game because it leaves a huge hole on d5.
GM Mikhalchishin put out a CD video on this line a few years ago claiming it can be efficiently used by white if he wants to avoid a ton of K-Indian theory by focusing on plans and ideas instead of memorizing reams of analysis. He gave the CD the catchy and misleading title Play the King's Indian Defense with g3 in 60 Minutes. What I found amusing was that he then broke his discussion down into 12 parts. Let's see, that's 5 minutes per part which doesn't seem like a lot of time even if you're just going to learn a system and the associated ideas.
He stated that when white faces the K-Indian or the Gruenfeld he has three approaches. First, try to out-prepare his opponent in the main lines, second, play one of the space-grabbing lines such as the Saemisch or third, fianchetto the B which imposes the type of game upon black that he's trying to avoid. This approach gives white a variety of very flexible plans, based more on principles than on specific moves. One reviewer wrote, "...with so much information, a second viewing will undoubtedly be desirable, however the fact remains that the viewer has a very rich presentation in the opening..." So much for the 60 minute claim.
The following old game, Kan vs. Boleslavsky, Moscow 1952 shows black using the ...d5-d6 combined with the ...f7-f5 strategy.
Ilya Kan (May 4, 1909 – December 12, 1978) was a Soviet International Master who played in ten Soviet Championships. His opening theory contribution was mainly in the flexible Kan Variation of the Sicilian Defense: 1.e4 c5 2.Nf3 e6 3.d4 cxd4 4.Nxd4 a6.
In this game Kan chooses the finachetto method of meeting the K-Indian. This way of meeting it is not the most challenging, but its advantage is that most of the time black does not get the sort of counterplay he hopes for when playing the K-Indian. The disadvantage is that in order for it to be effective white must possess some positional skills to capitalize on his small advantages. Here though, thanks to Kan's failure to appreciate the potential in black's position, he does not meet Boleslavsky's threats in the best way and gets badly outplayed. A most instructive game.