If one was to ask which member of the Axis was the last to remain at war how many would answer Japan? In fact it was Italy. In 1943 Italy did not surrender she requested an armistice. An armistice is a pause in the fighting and technically the two sides remain in a state of hostility (just as has happened in Korea) until a peace treaty is signed. A peace treaty was not signed until 1946. Germany and Japan both surrendered. This is why Italy was never part of the Allies and fought the Germans as a co-belligerent. What difference did it make? You may ask. A very substantial one if you were an Italian POW. Even though Italian forces were fighting alongside British ones from 1943 Britain could legally keep Italian POWs in captivity and force them to work on the land and did so in large numbers.
Interesting, didn't know this. Anecdotally - When I lived in the then-Czechoslovakia, I was told that the country couldn't divide, as an independent Slovakia would still be at war with Britain, having somehow omitted to sort things out at the end of WW2 (in fairness, they had a lot going on just then). A few months later? Voilà, independent Czech Republic and Slovakia. I did wonder if I should get the bus to Bratislava to demand unconditional surrender...
