Is 39 moves the longest a chess game can go moving only pawns? I've thought of a few different ways a chess game could go on moving only pawns, but I've only counted moves in one scenario:


*

*Both White and Black take 16 moves to line their pawns at the middle of the board.

*With a series of orderly captures in 8 moves, White and Black each wind up with 4 pawns each.

*Taking care to threaten the rooks first, White and Black move their pawns within striking distance of the opponent's non-pawn pieces. This would take 16 moves (bringing the total up to 40), except that...

*As soon as a White pawn threatens the Black king, Black would be forced to move the queen, a bishop or a knight to protect the king.


Have I thought through this scenario correctly? And even if I have, might could there be a scenario in which moving something other than a pawn could be put off longer?
 A: Edit: This is an improved version of my previous 39-move solution (using Ross Millikan's suggestion to let the pawns advance as far as possible befrore being captured).


*

*c3 b6  

*c4 b5 

*c5 b4  

*c6 b3 

*g3 e6 

*g4 e5  

*g5 e4  

*g6 e3  

*axb3 dxc6  

*fxe3 hxg6  

*h3 a6  

*h4 a5  

*h5 a4  

*h6 a3  

*h7 a2  

*hxg8N axb1N  

*b4 g5  

*b5 g4  

*b6 g3  

*b7 g2  

*bxa8N gxh1N  

*b3 g6  

*b4 g5  

*b5 g4  

*b6 g3  

*b7 g2  

*bxc8N gxf1N  

*e4 c5  

*e5 c4  

*e6 c3  

*e7 c2  

*exf8N cxd1N  

*e3 c6  

*e4 c5  

*e5 c4  

*e6 c3  

*e7 c2  

*d3 f6  

*d4 f5  

*d5 f4  

*d6 f3  

*exd8N f2+

A: You can do better by having pawns move more before being captured.
1-4   b2-b6     g7-g3
5     hg        ab
6-9   g3-g7     b6-b2
10    g7xh8N    b2xa1N
11-15 g2-g7     b7-b2
16    g7xf8N    b2xc1N
17-21 a2-a7     h7-h2
22    a7xb8N    h2xg1N
23-26 e2-e6     c7-c3
27    dc        fe
28-31 c3-c7     e6-e2
32    c7xd8N    e2xd1N
33-37 c2-c7     e7-e2
38    f2        e2xf1N
39-42 f3-f7+    d7-d3

