Assuming I was the general who decided when we'd attack, I'd send n messengers each with a c chance of getting captured, yielding a (1 - c^n) chance of the othe

Assuming I was the general who decided when we'd attack, I'd send n messengers each with a c chance of getting captured, yielding a (1 - c^n) chance of the other general attacking at the same time. By adjusting for n, I could have whatever probability of success I wanted, though never a guarantee of success. One can calculate the chance of losing data stored redundantly on multiple disks due to disk failure the same way, assuming that disk failures occur independently of each other, as they might for a large internet company with the data stored across multiple data centers.