The qualities of chess consists mainly of a special role of the king. If a check is declared, the very first thing needed is to defend the king. At the same time, another piece can be attacked without excess consequences or counterattack. If there is no way to save the king from a check, then the game is over and it doesn't matter if either side had a better position. The special role of a king is best shown in the case of a stalemate, a perpetual check, or whatever.
Paul Keres
White to move and mate in four:
White to move and draw:
Shamkovich - A. Polyak
Leningrad, 1953
White to move and win (mate in two):
During a castling attack it is often necessary to sacrifice pieces or pawns with the purpose to break down your opponent's pawn protection. Let's take the game Batuev - Abdusamatov for an example (diagram below). It is white to move and win: 1.Bxh7+ Kxh7 (or if 1...Kf8 then 2.Bh6!) 2.Bf6! Bxf6 (if the pawn captures the bishop with 2...gxf6, then white simply plays 3.Re3 and everything is downhill for black) 3.exf6.
Batuev - Abdusamatov
USSR, 1951
White to move and win:
Kan - Abramowski
Leningrad, 1951
Can black play 1...Bxg2?:
White to move and win:
Diagram #7
White to move and win:
Reshevsky - Boleslavsky
Zurich, 1953
Black to move and draw: