(Q was unresolved) So correct me if I'm wrong but I don't know a lot about history but I believe the axis powers consisted of Germany, Japan and Italy. I was asking my Grandad who's a qualified historian what it was like after the war and how did people get back together and how countries rebuilt bridges that had been burnt and he mentioned that he believe somewhat through sport and informed me that the first Olympics after the war was 1948 showing that they wasted no time getting back to normal and I was curious as to if the axis power countries attended and noted that Italy did attend and was invited whereas Germany and Japan were not why is this?
In early January 1945, still during the war, the Executive Committee of the IOC said that Germany and Japan would be invited to the 1948 Olympics, if they were politically and economically recognised. However, in 1946, it was already clear that Germany and Japan were unlikely to be invited.
As 1948 approached, Germany didn't fulfil these criteria - there was no German government, and the country was still divided into four occupation zones, the Soviet zone, which would become East Germany (DDR) and the three occupation zones of the Western Allies, which would become West Germany (BRD). West Germany and East Germany were formed in 1949, in May and October respectively, and Germany was invited to the 1952 Olympic Games. The IOC insisted on a single German team representing both Germanies. East Germany declined to participate, and only West German athletes represented Germany in 1952.
However, the IOC appears to have been more or less willing to allow German participation. In 1946, the IOC listed Germany in its list of National Olympic Committees (NOCs), although without an address. This was despite no official German NOC committee existing. The German Olympics working committee proposed the formation of an NOC to the American military government in December 1946, only for that proposal to be rejected in February 1947. A German NOC was finally formed in September 1949, the day after the newly-elected federal government took power.
Britain strongly opposed the invitation of Japan, on the grounds that Japan was still, on paper, an enemy combatant. Japan's peace treaty with the Allied powers was only signed in 1951 (and took effect in 1952 in most countries). However, the official reason given by the IOC was that neither Germany nor Japan had an NOC.
As far as I can tell, Japan had a functioning NOC as the 1948 games approached, but the IOC simply refused to recognise it.
Israel (which had requested an invitation) and Bulgaria were also not invited for the same reason - Israel's NOC was recognised in 1952, and Bulgaria's NOC was re-established in 1952 following its disbandment in 1944. East Germany's NOC was recognised in 1955 (the year in which the Soviet Union officially granted sovereignty to the DDR), but as the representative of the geographical region of East Germany and not as the representative of an East German state, avoiding the question of recognition of the DDR. However, in 1956, the two Germanies formed a combined team for the Olympics (which didn't stop East Germany beating its chest about East German gold medals). The combined both-Germanies team continued through to 1968, when the East German NOC was finally recognised as a national NOC, and East Germany participated as a separate country in the 1972 Olympics.
(Germany finally signed a peace treaty in 1990.)
Further reading:
J. Buschmann and K. Lennartz, "Germany and the 1948 Olympic Games in London", Journal of Olympic History 6(3), 22-28 (1998). http://isoh.org/wp-content/uploads/2015/04/30.pdf
Beck, Peter J. (2008) "The British government and the Olympic movement: The 1948 London Olympics". International Journal of the History of Sport, 25(5), pp. 615-647. http://dx.doi.org/10.1080/09523360701875566