Can someone explain, in detail, what exactly happened before the Civil War in Skyrim.

How long has it been raging? I've been under the impression that the only casualty was Torygg, and it wasn't until Ulfric escaped Helgen that actual battles occurred.

How did Torygg become Jarl and High King? His father was High King before I know, but the Moot has to decide right? Surely Ulfric didn't vote for Torygg if he kiled him.

Was the duel traditionally acceptable, or murder?

I want every piece of detail on it.

From what I understand, Torygg had been High King long before this thing happened. He, from what people tell you, was all about the Empire, "The Empire this, and the Empire that". Torygg likely did sympathize with Ulfric's words, but Ulfric, who was a veteran of the Great War 30 years prior, was sick of talking, he wanted action. Torygg, as some say, would have been glad to listen to Ulfric and work with him, but Ulfric wanted none of it. How did Torygg become High King? Simple, the Moot agreed that he'd become High King. What could Ulfric do if the rest of the Jarls were for Torygg? But that was ages ago, likely even from before the Great War itself!

The duel is whatever you make of it. Some say it was fair and honored ancient traditions. Both men stood up, fought, and Torygg lost because he was weak. Others say it was straight up murder, that Ulfric "simply walked up to [him] and murdered him" with his voice. Stormcloaks believe it was fair combat. Imperials think it was murder.

I always assumed the civil war had been raging for months, and it had crawled to an absolute stalemate. The capture in Helgen was the biggest break the Imperials had in a long time.

To me this is a major failing of game mechanics.

If you don't pick a side and do the CW questline, there is no physical evidence of a War going on.

Apart from the (very rare) small fight between half a dozen S/Cs & Imps.

I always thought that once Torygg kicked the bucket the Civil War consisted mainly of minor skirmishes until the Battle of Whiterun.