Major Dartnell had his mounted division patrolling in the vicinity of the Mangeni River when he located a regiment of Zulus. It was then Lord Chelmsford divided his 3rd Column to reinforce Dartnell, and of course as any Zulu War enthusiast knows, that's when the Zuluas attacked the British camp at Isandlwana. And then other Zulu regiments attacked Rorke's Drift.
So all three changes to my map are directly related to the Battle of iSandlwana, and the subsequent battle at Rorke's Drift. So here's the map. Can't wait to see how it looks in the book.