Nasi promoted a moral reformation of the military and civil administration and he showed notable skills in dealing with indigenous chiefs.

After the beginning of World War II, Nasi led the Italian conquest of British Somaliland in August 1940.

On 6 July, after Duke Amedeo of Aosta and Generale Pietro Gazzera surrendered, Nasi became the acting Governor-General of Italian East Africa.

Although Nasi was listed as a war criminal by the post-war Ethiopian government, Italian historian Angelo Del Boca, usually very severe in judging the behaviour of the Italian army in the colonies, considers him the best officer of the Regio Esercito in East Africa.

Solomon Getahun supports this view of Nasi, noting that his behaviour towards the inhabitants of Gondar and the adjoining territories helped him to sustain the fight against both British and Ethiopian forces as long as he did.