user9162: Interesting puzzle that is quite hard to stop.

user15: I think it is 5 moves.
[FEN ""]

1. a3 e5 
2. a4 e4
3. a5 e3
4. a6 Bc5
5. axb7 exf2#

You can't do it any shorter as you need at least 4 moves to get your pawn to the 2nd line where it can checkmate the white's king and one more move to bring a supporting piece (queen or bishop), so the white king wouldn't be able to capture your pawn.

user3831: 4 moves, as far as I can tell.
[FEN ""]
1. e3 e5 2. Ke2 Qh4 3. Kf3 d6 4. Qe2 e4#

Another one:
[FEN ""]
1. d3 d5 2. Kd2 e5 3. Kc3 Be6 4. Qd2 d4#

And one more:
[FEN ""]
1. e3 e5 2. Ke2 d5 3. Kd3 Qf6 4. Qe2 e4#

Same theme for all of them, really.

9162: <p>Interesting puzzle that is quite hard to stop.</p>
 15: <p>I think it is 5 moves.</p>

<pre><code>[FEN ""]

1. a3 e5 
2. a4 e4
3. a5 e3
4. a6 Bc5
5. axb7 exf2#
</code></pre>

<p>You can't do it any shorter as you need at least 4 moves to get your pawn to the 2nd line where it can checkmate the white's king and one more move to bring a supporting piece (queen or bishop), so the white king wouldn't be able to capture your pawn.</p>
 3831: <p>4 moves, as far as I can tell.</p>

<pre><code>[FEN ""]
1. e3 e5 2. Ke2 Qh4 3. Kf3 d6 4. Qe2 e4#
</code></pre>

<p>Another one:</p>

<pre><code>[FEN ""]
1. d3 d5 2. Kd2 e5 3. Kc3 Be6 4. Qd2 d4#
</code></pre>

<p>And one more:</p>

<pre><code>[FEN ""]
1. e3 e5 2. Ke2 d5 3. Kd3 Qf6 4. Qe2 e4#
</code></pre>

<p>Same theme for all of them, really.</p>
