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The assumptions here are that your opponent will block whenever you could win on the next move, and also that given the opportunity to force a win (by creating two different directions with two in a row) your opponent will take it, but that otherwise, your opponent's moves are random.

In that setting, your best strategy if you go first appears to be (1st move) take the center, (2nd move) move opposite your opponent, (3rd move) create two directions of two in a row (which will always be possibly unless your opponents first two moves were corners, in which case the game will tie - this is even true if your 3rd move is actually blocking - blocking will create a forced win for you).

What is your best strategy if you go second instead? Is there an opening move your opponent can make which would allow you, as second player, to force a win, instead of just a tie?

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  • That strategy for an opponent seems a little strange to me. A more realistic strategy would be to try, in order of priority to: (1) make a move if it wins immediately, (2) block a win on the next turn, (3) do a fork.
    – Hao Ye
    Dec 22, 2014 at 21:12
  • Simple second player strategy on first move - Don't take a side square. Ironically, this is also the winning First player strategy on first move.
    – Forget I was ever here
    Dec 22, 2014 at 23:36
  • After that for both players: Win if you can; block if you must; or fork if you can.
    – Forget I was ever here
    Dec 22, 2014 at 23:43
  • "A strange game. The only winning move is not to play." ~ WOPR
    – Andrew
    Feb 1, 2018 at 14:57
  • 1
    Have your children learned Nim yet?
    – Forget I was ever here
    Feb 11, 2018 at 1:48

2 Answers 2

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As you know, tic tac toe is a solved game that end in a tie with optimal play. And it's too short to really get any initiative as the second player, even for children. Going second there is no way to force a win without 2 misplays from the first player. So if you want a "strategy" for player 2, it really comes down to just not losing.

As for going first, I often liked taking a corner first because it offers more opportunities for my opponent to mess up (any square but the middle is a win for the first player with perfect play).

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-1

If you are second, you will tie or lose automatically, unless your opponent is severely distracted or lets you win. In the following examples of moves and your responses, X moves first and each column is a set of two turns.

Example 1.

x o - | x o - | x o -
- - - | - o - | - o -
- - - | - - x | o x x

Example 2.

x - o | x - o | x - o
- - - | - x - | o x x
- - - | - - o | - - o

Example 3.

x - - | x - - | x x o
- o - | - o - | - o -
- - - | - o x | - o x

Example 4.

- x - | - x o | - x o
- o - | - o - | - o -
- - - | - - x | x o x

Example 5.

- x o | - x o | - x o
- - - | - x - | x x o
- - - | - o - | - o -

Example 6.

- x - | x x o | x x o
- - - | - - - | - o -
- o - | - o - | x o -

Example 7.

- - o | x - o | x - o
- x - | - x - | o x x
- - - | - - o | - - o
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  • 1
    I tried to salvage the post as good as it gets, however I still have to downvote it because I'm not sure what they're trying to say (whether it's supposed to be best practice, examples of turns that won't lose you the game, or simply examples of turns you could take). At least it should be somewhat readable now...
    – TheThirdMan
    Mar 22, 2017 at 10:47
  • The answer seems much more legible like this -- I'm going to do a bit more editing.
    – doppelgreener
    Mar 22, 2017 at 12:02
  • In your example 2, player 2 (o) has lost against a good player 1 (x). Player 1's second move would be bottom left, forcing player 2 into middle left; player 1 then goes bottom right giving two options for a win (centre or bottom middle). You are therefore not showing good strategy for player 2!
    – AndyT
    Jul 20, 2018 at 13:31

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