The people of Israel left Egypt in haste and replete with Egyptian wealth around 1491BC and arrived at the edge of the promised land in 1490BC. There were 603,550 men over 20 (Numbers 1) and so total estimate over 2 million exited. Precisely this number 603,550 died as Numbers 14:29 tells us, confirmed in Deuteronomy 2:14-16. Because of their unbelief and fear, believing the cowardly report of ten of the spies, they did not enter the land but were made to wander in the wilderness of Sinai, albeit sustained by God’s provision for nearly 40 years and they were buried there. The people only began to come into their possession in 1450BC under Joshua. It is incredible that so long a time, indeed a lifetime for the adults who left Egypt, and clearly a significant and full time (10×4) could be spent going nowhere!
Notable is the fact that God hardened the hearts of Sihon and Og (as he did with Pharaoh), the first two kings whose people were utterly defeated and destroyed by the Israelites. It is clear all three first hardened their own hearts and God just confirmed and strengthened that hardening (Exodus 9:34-10:1). Note that during the conquest, men, women, and children were killed in their pagan reprobate state just as all will be condemned on the last day who lived and died in sin, not being elect according to God’s good pleasure. Also worth remembering that the reprobate among the Israelites, perished similarly in the wilderness, because of their unbelief and disobedience! They were church members!