Why it is so strong
The d5 pawn is passed and protected by the pawn on c4. The black king can never capture it, and it must stay close enough to stop it from advancing. White's king, meanwhile, is free.
If the black king ever goes after the c4 pawn, the d-pawn runs. It is a permanent weakness for the defender, and it lasts as long as the pawns stay put.
The plan here
Material is level, because Black has a passed h-pawn. White's king has to stop that pawn, win it, and then return.
Ke4 is the only winning move. The king stays inside the square of the h-pawn and keeps the black king out of e5. After Ke3 instead, Black plays Ke5 and the game is drawn. Kc3 and Kc2 even lose, because the king leaves the square of the h-pawn.
Typical mistakes
Do not give the defending king an active route. The protected passed pawn is strong because the black king is stuck; let it into the game and much of that strength disappears.
When the black king does take the c4 pawn, push the d-pawn at once. In the demonstration, d6 is the only winning move: the pawn promotes before the black c-pawn can.
Remember
- The enemy king cannot take it
- It ties the king down
- Your king is free to roam
- If the king leaves, the pawn runs