suicide attack done at the exact right place.
in the game I am playing now, I did a mistake with india (put the army in burma), so japan declared in J2, hit killed my burma army (took a few planes as losses), he took shan state with 1 inf and had 4 inf +3 art +1 tank in kwangsi, where he also had built a port and AB.
His fleet was placed so that blocking was imposible.
I managed to avoid disaster by strafing shan state with my 3 planes, china took yunnan, lone ANZAK inf took shan state, so now his planes could not land anywhere
and 2 UK inf in hong kong attacked kwangsi, rolling 1 hit.
the combination of reducing his attack from 19 to 8 planes, and killing 1 inf was just enough to make his attack on india to bad (40% ish, with the extra inf his losses in india would have been about 10 IPC less if he had tried).
the thing about supprise moves is that they are only something to use against bad players, I have always been one for meticulous planning and conservative gameplay.