JW Rogue I think the JW religion would have continued on a similar track with or without WW1 starting in 1914.
The prophesied date of 1914 according to Russell (who borrowed his ideas from others) was to have been the latest date for the destruction of all God's enemies and the restoration of the Earth under Christ's rule. Most significantly though, and with great financial consequences, it was also promised to see the visible return of Christ.
By the end of the nineteenth century The Russellites had been just a local affair around Pittsburg but so I have read, announcing the actual date for the "second advent" of JC was Russell's special baby which began after the turn of the century. It was publishing this prophecy which brought fame and attention for Russell from the whole world as a syndicated preacher.
It was a great disappointment for Russell and co and a public failure of his credibility but he postponed the date, as all doomsday merchants have to, to 1915 and as ever , to no effect. He did announce to Bethel that the world had in fact ended...like you do.
It was only later probably in Rutherford's gloss on Russell's predictions that the mention of 1914 was seen to be a divine insight. Rutherford's WT in the twenties, I believe began the idea...and the Watchtower always builds castles on its own myths.