Thursday Code Puzzler: Two Generals

By now you should be familiar with our Thursday Code Puzzler slot. The idea is simple: solve the coding problem as efficiently as you can, in any language or framework that you think is suitable.

Note: Even though there really is nothing stopping you from finding a solution to this on the internet, try to keep honest, and come up with your own answer.  It's all about the participation!

The Two Generals Problem

This week's problem is another classic computer science puzzle that is designed to deal with communication protocols. The problem statement is as follows

Two armies, each led by a general, are preparing to attack a city. The armies are encamped outside the city on two mountains separated by a large valley. In order to capture the city, the generals must attack at exactly the same time. The only way for the generals to communicate is by sending messengers through the valley. Unfortunately, the valley is occupied by the city's defenders, so there's a chance any given messenger will be captured. Each general has no way of knowing if their messenger arrived. How do the generals coordinate their attack?