Problem diagram.
White to invade the upper right.

Source:
Attack and Defense, Ch. 7, p. 162
Akira Ishida & James Davies, Ishi Press

Solution follows    (or click here to download SGF)

Correct.
White 1 and 3 is a classic invasion sequence. White holds A in reserve and threatens B to sandwich Black's group against the marked White wall.

Continuation diagram.
After Black blocks at 4, White slides to 5. Blocking again at 6 is the best that Black has. White's forcing sequence through 15 is a success, especially because White threatens to cut at A.

Black variation.
Trying to cut off White's group with 6 and 8 is bad. White lives through 11, but now threatens White A, Black B, White C. White's invasion has been a big success.

Hits: 504