the 3 pawn center i would be worried about if i started the hippo with 1.g6 is not CDE but DEF. white doesnt have to erect it right away either. for example, play be3 first to give white the option of the qd2 f3 formation if you try to switch to a modern.
Hippopotamus Defence

the 3 pawn center i would be worried about if i started the hippo with 1.g6 is not CDE but DEF. white doesnt have to erect it right away either. for example, play be3 first to give white the option of the qd2 f3 formation if you try to switch to a modern.
Black should have No Worries!
The Pirc Defense has come a long way!
The White Austrian Attack isn’t as powerful as it used to be!
Same move order as below:
A Pure Transposition from the Modern Defense into the Pirc Defense.
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Obviously, People are terrified of Old Ghosts.
The Austrian Attack has put the Fear into many of Foe’s, but we are in 2025!
Should Black really be afraid?
I think the Australian Attack has been on the decline.

It's great to see two strong players on the Hippo thread discussing transpositions to take on the Austrian Attack. In Simon William's Hippo course he thinks if you can sail through those waters competently the rest should be plain sailing. Learning some good solid lines from the Modern or the Pirc can only help! 👍
Has anyone tried both move orders?
Yes, and it is easier to reach the full Hippo using the 1...b6 approach.
edited for clarity:
However both 1...g6 and 1...b6 can suffer from an early push of a white center pawn. For example 1.e4 g6 2.d4 Bg7 3.e5, when Black will be unable to develop his d-pawn to it's Hippo square of d6 without risking the possibility of compromising the center.
The double fianchetto also suffers greatly from early center pawn advances and is therefore not a good way to initiate a Hippo build.
Against 1.e4 I play 1...d6 and vs 1.d4 I play 1...e6 and then develop the other center pawn. Once the center is secure, build Hippo reactively. The Hippo king is safer in the center for longer than with most other openings. Therefore, castling is not an urgent issue and can sometimes be omitted altogether when the king becomes a more active defensive as well as offensive piece in the middlegame.
This is usually the case when playing the full Hippo.
I disagree!
When Black plays 1…g6, The line is the Modern Defense. The Hippo hasn’t manifested itself, yet!
The moves 1.e4 g6 2. d4 Bg7 3.e5 would certainly lead to White being punished in the Modern Defense.
Black wouldn’t need to go into a Hippo in such situation because he would be able to punish White for his pawn over extension.
Using the Modern Defense as the “Starting Hippo Move Order” helps punish players who try to get cheeky.
Against the Hippo, White side players aim for those 3 pawn set ups to beat up on the Hippo, but due to Black initial opening which is Modern.
White doesn’t have the luxury to bully the Hippo because the Modern Defense makes short work of aggressive players which is why I have always liked using it.
For Example:
In the above position, White played 3 pawn center. The Hippo might have trouble against a 3 pawn center above, but the Kings Indian Defense doesn’t and Black has the power to transpose into a favorable position to deal with what White is doing!
In the above position, White played 3 pawn center. This time with the f4 vs. c4 pawn.
The Hippo might have trouble against this formation, but the Pirc Defense doesn’t!
The Pirc Defense has came a long way and it has ways of dealing with the Austrian Attack.
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When you actually look at the situation, What can White actually do against you?
The Modern Defense gives Black the flexibility and speed to castle fast so that it always has the answers and flexibility to adapt!
Most times players playing White continue normally because Black has all the answers!
The above position is the standard position you will reach countless of times because White players already know their cheap 3 pawn center tricks don’t work!
In this position, White often plays 2 move!
5.Qd2 which set up a Battery and allows Black to play b5 gaining space + creating a pawn storm on Queen Side
or
5.a4 which aims to stop Black b5 Queen side aggression!
However, in the process of play a4, White slows down his development and walks right smack into the Territory of the Hippo!
Hippo can be very dangerous animals when they feel threatened and Black can play b6 instead of b5 aiming for a Hippo Transposition!
The b6 isn’t even the only move Black can play to aim for Hippo!
I have even tried the curious move Nd7.
The move Nd7 introduces the idea of e5 which would have 3 attacks. Most people respond with Nf3 adding an extra defender.
At which point, Black has tricked White into a 2 pawn center and the Hippo Transposition is live!
I really feel like White options get manipulated!
White moves first and it seems like White has all the freedom with endless opportunities, but when you really look at the situation.
White can’t stop Black from having a good position. Black has answers to every move White does!
It does make a person wonder if with best play the game is draw!
If I missed something, Feel free to let me know! This is just what I have seen so far, studied, and played.