This Parashah begins the last of the Five Books of The Torah, Sefer Devarim. This Book is also called Mishneh Torah, literally 'the Repetition of The Torah (and hence the Greek/English title of Deuteronomy). Sefer Devarim relates what Moshe told the Beney Yisrael during the last five weeks of his life, as they prepared to cross the Jordan into Erets Yisrael.
Moshe reviews the mitsvot, stressing the change of lifestyle they are about to undergo: from the miraculous, supernatural existence of the desert under his guidance to the apparently natural way of life they will experience under Yehoshua's leadership in Erets Yisrael.
The central theme of this week is the sin of the spies, the meraglim. The Parashah opens with Moshe hinting to the sins of the previous generation who have died in the 40 years of wandering in the desert. He gives the Beney Yisrael a description of what would have happened if they hadn't sinned by sending spies into Erets Yisrael. He tells them that HaShem would have given them all of the land from the Mediterranean to the Euphrates including the lands of Amon, Moav, and Edom without needing to fight. He details the subtle sins that culminate in the sin of the spies, and reviews at length the sin of the spies and the results of that sin: the entire generation was to die in the desert, that Moshe would not enter Erets Yisrael, but rather they would be led by Yehoshua bin Nun. He reminds them that their immediate reaction to HaShem's decree was to want to 'go up and fight' to redress the sin. He recounts how they wouldn't listen when he told them not to go because they no longer merited to vanquish their enemies miraculously. They ignored him and suffered a massive defeat. They were not allowed to fight with the kingdoms of Esav, Moav or Amon -- these lands were not to be part of the map of Erets Yisrael in the meantime. When the conquest of Canaan will begin with Sichon and Og, it will need to be in the natural way of warfare.