White castles short (ie. king's side), bringing his king's rook into
play for 6.B-Kt3, 6.R-K1 or
6.P-B3. Black also castles, planning 6..P-Q4 or
6..P-Q3. White usually has a small advantage.
White Black
1. P-K4 P-K4
2. Kt-KB3 Kt-QB3
3. B-B4 Kt-B3
4. P-Q3 B-K2
5. 0-0 0-0