| 4. ........ | B - Kt 5 |
Black replies in the same manner, threatening a possible exchange of Bishop for Knight with Kt × P to follow.
| 5. O - O |
an indirect way of preventing 5...B × Kt, which more experience or study will show to be bad. At the same time the Rook is brought into action in the centre, a very important point.
| 5. ........ | O - O |
Black follows the same line of reasoning.
| 6. P - Q 3 | P - Q 3 |
These moves have a two-fold object, viz.: to protect the King's Pawn and to open the diagonal for the development of the Queen's Bishop.
| 7. B - Kt 5 |