The book, "The history of the decline and fall of the Roman Empire" by Edward Gibbon is a classic, and is a free iBook. It is very detailed on historical events and tends to just give the facts. Even though it was written over 2 centuries ago, it is reader friendly.
it seems different people interpret the history and give different reasons for the fall of the Roman Empire. For me it is obvious. It had almost all of its success as a Republic, before it became an empire. When Hannibal attacked, pillaged Italy, wiped out armies, and inflicted humongous casualties, the Roman citizens remained amazingly united, and kept raising new armies, incurring huge sacrifices, until they won. In the days of empire, the participation of Italians in the legions steadily decreased, until in the later stages there were virtually none, and the Legions were primarily made up of Germanic and other peoples who were just there for the money. In short, once the Roman citizen had lost his say in the Government, he was less interested in defending it.
Linking this back to Watchtower: Watchtower also does not give its rank and file any say. I think for that reason alone, it has a limited lifespan. I have a suspicion that, for example, if its finances take a turn for the worse, the rank and file won't bail it out.
