"He is a child. He will slow us down. Another mouth to feed? It is already hard enough to find food. He is too young to do any real work-he'll be of no help to us" (Park 21)
"He should be somewhere nearby...I don't remember if he slept near me-I was so tired-perhaps he has gone near me-I was so tired-perhaps he has gone to find something to eat-...'I am sorry.' he said again" ( Park 38 )
"'No, Salva. I am going to take you to the refugee camp, but then I will return to Sudan, to fight in the war'... 'Uncle when you go back to Sudan, you might meet my parents somewhere'" ( Park 60-61 )
I'm sorry for leaving you nephew... I must fight in the war!
This situation is external because the group was specifically addressing that Salva wasn't good enough or wasn't able to survive through the obstacles they will go through. They don't need another circumstance to slow them down.
Salva and the group of Dinkas were sleeping in the shelter they made until Salva lost Marial to a tiger. Marial was Salva's source of positivity and happiness, now that he is dead, Uncle will be the one to comfort the small boy. Marial used to be his hope and optimism but now he has to deal with it on his own with Uncle on his side.
Uncle was going to leave Salva alone until he arrived at the Refugee camp because Uncle needs to continue fighting in the war. This affects Salva because he will be isolated during the rest of his travels.