[dilipd]

Correct! Repeatedly slapping Japan was reasonable because of Japan's imperial ambitions, e.g. Taiwan(1895), Manchuria(1905), Korea(1910) etc. And, England and some other European countries were not 'repeatedly slapped', even though they were also imperialist, may be far longer, may be far worse!

[vkou]

Japan was also promised the world for their support of the Entente in World War I - and, much like Italy, received nothing for its efforts.

Let's not forget the context of their imperial ambitions - in the first half of the twentieth century, most of the world was still ruled by empires.

[tankenmate]

Actually Japan was mandated large amounts of German New Guinea by the Treaty of Versailles and the South Pacific Mandate; Palau, almost all of Micronesia, and parts of Papua New Guinea. Other parts of German New Guinea were ceded to Australia, New Zealand, the US, and Britain. France of course kept their South Pacific colonies.