I've read on Elder Scrolls Wiki that Tulius is general of the 4th Legion. Where does this info come from?

http://elderscrolls.wikia.com/wiki/General_Tullius

Never ever ever ever use Elder Scrolls Wiki for lore. Ever.

If you want to know something about lore, go to http://www.imperial-library.info/storyboard/elder-scrolls/lore-forum first and http://www.uesp.net/ second. UESP isn't always 100% reliable, but Elder Scrolls Wiki just completely makes stuff up sometimes.

That said, I have no recollection of any "General of the IV Legion" thing.

Hes actually the general for the 19th legion.

Legion 1-11 and 13 are in cyrodill
Legion 14-16 and 20 are in high rock
Legion 12 is at the left side of morrowind, backing up legion 19.
Legion 17,18, 21 - 32 got destroyed during the great war.
Legion 19 is at skyrim.

TES wikia killed my dog.

Seriously said Titus II was the son of Titus I. Seriously. After 160 years since the novel.

tes wikia quite literally took our jobs, and is now svcking at them.

TIL for lore related documents, UESP for game-related articles, and the Lore forum for clarifications and primary sources.

And TES Wikia when you have some brain cells to kill off.

Alcohol is more fun for doing that

Hell, a nine-inch drill in the ear is more fun for doing that.