A shogun was a general. For a few hundred years that was all the word meant: a commander the emperor sent to fight on the northern frontier. Then, in 1192, a warrior who had won a civil war took the title and kept it, and for most of the next seven centuries the real government of Japan was a shogun’s. The emperors stayed in Kyoto, honoured and powerless, until 1868.
This site tells that story in short pages, one for each period. Start with the word itself, or pick a period below.