"ויהי אחרי מות משה עבד ה..."
And it was after Moshe the servant of Hashem died...
Rashi explains why the following Pasuk says "משה עבדי מת...," Moshe My servant haso died. Here's a link to the Rashi. http://m.chabad.org/library/bible_cdo/aid/15785#showrashi=true
Summary: "If Moshe were still alive, I [Hashem] would prefer him." It's referring to Moshe as the law-giver, not the leader. Moshe gave 3,000 laws that people forgot. Yehoshua` want to know them, so he asks Hashem. Hashem says, "Moshe my servant has died. The Torah is called by his name, implying that you cannot possibly understand it. Go out and occupy them with martial activities."
My question is: Why is the beginning of 1:1 necessary?