1) Joshua led the Jews into the Land of Israel in 1272 BCE to conquer the land. 2) As in Megillat Esther (9:19): ''Therefore, the Jews...living in UNWALLED cities celebrate the 14th day of the month of Adar,'', but doesn't say when those in walled cities should celebrate Purim. The Talmud (Megillah 2b) concludes that walled cities should celebrate on the 15th of Adar, just like Shushan, a walled city, did at the time of Purim (the battle against the enemies of the Jews in Shushan lasted one day longer than the war in other cities, and thus the victory was celebrated there on the 15th rather than the 14th - see Esther 9:15). Why should the status of a city be based on whether it had a wall at the time of Joshua's conquest rather than whether it had a wall at the time of the miracle of Purim? There are two main reasons given: a) Had it been based on whether a wall existed at the time of Purim, the great cities of the land of Israel would have to be classified as unwalled cities, because their walls lay in ruins at the time of Purim, due to the Babylonian conquest. So, by making it the time of Joshua, the cities of the land of Israel received the honor of reading with the walled cities (Jerusalem Talmud). b) Since it was Joshua who led the first battle against Amalek when the Jews left Egypt (Ex 17:8-16), the sages felt it appropriate to associate his name with the celebration of the downfall of Amalek at the time of Purim (Haman was a descendant of Amalek). 3) The Kitzur Shulchan Aruch is (of course) referring to his place and time - the Jewish communities in Europe in the late 19th Century CE.

1) Esther 9:22 2) Isaiah 57:16