Before colonialiam Uganda was a much larger entity than we know it today.
1.) Juba, South sudans capital city was part of Uganda.
2.) The Northern part of Turkana, up to midway Lake Rudolph (Lake Turkana), was part of Uganda, it was given to Kenya in 1926
3.) The entire Lake Albert and a strip of terriroty on the other side of the lake was in Uganda (part of Bunyoro and was only transferred to Congo(D.R.C) by the brussels convetion 1910.
4. Most of Kigezi, Kasese and all of Lake Edward were in congo, only transfeered to Uganda in the same treaty, whose agreement was not signed till 1915.
5.) The people east of Kabale – in places like Maziba and Kikagati – were in German East Africa (Tangayika, Tanzania), only joining Uganda in 1910.