From these positions, send your generals right after each other:
From A to
Camp 20) 100 Scavengers, 50 Stone Throwers
BLOCKING NORMAL general:
[197C (-)] {
140 - 200 seconds of fighting, 0.1% chance of 120 seconds}
Note that general B must be sent to the leader camp 22. He will be intercepted by camp 21, which is his real target.
From B to
Camp 22) 50 Scavengers, 50 Guard Dogs, 50 Stone Throwers (Camp 21)
BLOCKING NORMAL general:
[161C (-)] {
120 - 180 seconds of fighting}
From C to
Camp 22) 1 Skunk, 100 Guard Dogs, 80 Stone Throwers
BATTLE HARDENED general:
[89R 111S (66R - 78R - 89R)] {40 seconds of fighting}
VETERAN general:
[87R 163S (66R - 77R - 87R)] {30 seconds of fighting}
The marching time for general C, from the moment general A starts his battle, till the moment general C starts his battle, is 70 seconds (21 steps marching) plus the time it takes to send off generals B and C, some 5 seconds each. If general C is a battle hardened general, his total time of marching and fighting will thus be 70+5+5+40 = 120 seconds. Since there is an 0.1% chance that the blocking general A will fight for only 120 seconds, this block is rather tight. If possible, try to send generals B and C within 4-5 seconds from sending the previous general. If for some reason you do notice that one general has been sent off a little late, do recall all of them and resend.