Good book on the subject: Khubilai Kahn’s lost fleet by James Delgado
From it; a couple of additional reasons for the invasion of Japan were that they were enemies of the Koreans, Kahn’s new allies, and had a substantial trade with Song china before Kahn managed to successfully conquer it.
So the Mongols invaded for (a) Song?
I wonder if the “ElDorado effect” may have helped motivate the Mongols to attempt an invasion of Japan. Koreans may have made up stories of great treasure in Japan as a ploy to get the Mongol army out of their hair.
Japan was for several 100 years the greatest source of piracy in Asia
by far. A Chinese name for ethnic Japanese was “dwarf pirates”.
I have read that Japanese pirate fleets were at times active to the
extent of dozens of ships acting effectively in unison to pillage
widespread mainland coastal areas. Even if they were a lesser scourge
in the 13th century, it may be that aggressive Imperialism was not
the main reason for the Yuan Dynasty attack on Japan: it could have
been a matter of legitimate retribution, not to mention self-defence.
Don’t forget the Ninja’s too. 
If there were enough Samurai this could have been an epic battle.
We there very many Samurai? I thought they were like our Navy Seals & Delta Forces. Highly trained, elite fighters. But there’s not very many of them.
It was the epic awesomeness of the PIRATE NINJAS that generated the unseasonal typhoons out of sheer AWESOMENESS!!!
Kami Kaze. That, my friends is REAL ULTIMATE POWER!!!1!!!1
Not exactly. Samurai were the landed warrior class in a society that wasn’t quite a caste system yet ( but would become one eventually ), but was verging on it. It wasn’t exactly a synonym for “warrior” or “soldier”, but it was closely associated with those professions. You can think of them as the equivalent of the landed nobility + gentry of Europe, ranging from the relative handful of major rulers to the masses of knights, a good number of them relatively impoverished, but still holding rank by right of blood.
They were elite in the sense that the military tended to be their dominant profession ( just as with their European equivalents ) and being of higher status they would often have had the money to afford higher quality arms, armor and training than your average schlub soldier. So they were elite in the sense of your average high medieval European knight, trained for warfare from an early age. They were not elite in the sense of Navy SEALs ( i.e. a tiny number of best of the best professionals ).
Eventually they did become a formal caste and the sole source of military force, as weapons were forbiden to all others. By then they formed maybe ~10% of society and thus could be relied on to form sizeable armies all by their lonesome.
That’s funny… He doesn’t look Jewish.