Read what you can see

In a hidden-army game you never see the other side’s ranks, but you see plenty: which pieces have moved, how far, and which ones stayed still all game. Each of those is a fact you can reason from.

A piece that moved more than one square in a straight line can only be a scout. A piece that has never moved might be a bomb or the flag — or simply a piece that has not been needed yet. Facts narrow the possibilities; they rarely settle them.

The same game was invented more than once: a version in Paris before the First World War, and similar games in China and the Philippines where a referee says only who loses each battle. People keep reinventing it because deciding with half the picture is a common human situation.