Стратего

Stratego by Jumbo is the most well-known of this type of hidden tactics board games. It was launched just after World War II in 1946 and has led to a variety of various themed versions and spinoff variations.

This game is very similar to, and almost certainly derived directly from, the Gibsons game L'Attaque who had acquired the UK rights in 1925 from the game’s creator Mademoiselle Hermance Edan who launched it in France in 1909. It is not exactly the same, but not far from it (numbered pieces, spy (same name) can kill the strongest piece but only when attacking, flag, bombs, etc.) The game in turn likely drew on various ancient Chinese board games such as Lu Zhan Jun Qi or the classic children's game Jungle.

From the box:

The gameboard is your battlefield. You have an army of men at your disposal and six bombs. Your mission--protect your flag and capture your opponent's flag.

Secretly place your men, bombs, and flag on the gameboard with these objectives in mind. But remember your opponent is doing the same thing, so you must plan a defense as well as an offense.

Once the armies are in place, advance your men. When you're one space away from an enemy, attack. You and your opponent declare ranks. The lower-ranking man is captured and out of play.