Part I: A Lecture about Leaning Attacks
For a very small fee (1€/lecture) you can watch and listen to a wide range of lessons on Go Juan's Internet Go School. The lessons are sorted by strength as well as by topic. They are basically lessons given using the KGS User interface. The one I want to recommend today is the first lecture on leaning attacks: http://internetgoschool.com/lecture.vhtml?ls_id=100. It is really really really good! The teacher is Shen Jing, 2P.
I came across this lecture in a time I lost game after game, because my attacks on weak groups lead to long and complicated running battles, ultimately ending with my opponent escaping in some unoccupied area on the board or connecting to another group. Watching the lecture was a strange and exciting experience. Everytime the teacher explained why a direct attack wouldn't work for position X and why a leaning attack would be advisable, I felt as if she was reviewing one of my games! It was exactly what I had been missing without knowing it. I think this lecture was one of the most important influences for leaving the 18-kyuish-times behind me and enter the era of being 15-kyuish :) I still can not play a single game without thinking about it several times. It had an tremendous impact on my game!
A leaning attack means basically that you attack one position (usually a stronger one) in order to gain strenght to then attack another one (usually the weaker). Diagram 1 below shows a nice example. It is black's turn. If he tried to just attack the marked stones directly, he would fail.
So he "leans" himself on white's group in the upper right. White now has two choices. Either strengthen the group under direct attack (See diagram 3) or run out towards the center with the p-13 group (see diagram 4). We will see that black profits quite a bit either way.
If white chooses to defend the group under direct attack, black can trap the p-13 group.
If white chooses to run towards the center, black conquers the territory in the upper right.
In order to get a better impressions of the concept I really recommend the lecture on Guo Juan's Internet Go School. Within the next days I will also discuss a game of mine that was really dominated by a leaning attack I launched in order to come back into the game. The game is still running on Dragon Go, so I will have to wait until after yose. I think I am going to loose, but it is a very interesting game anyways ;)
PS: The example used in this post was taken from here.