In Joshua, chapter eleven, verse eighteen, the conquest of Canaan was an extended series of campaigns lasting about five years. Joshua made war for a long time with all those kings. Though the victory is put together and lies in a small compass, the triumph is not at once. Nor in a few days, as were those of the five kings.
Caleb, a faithful man of God, was forty years old when Moses sent him out of Kadesh-Barnea as a spy. And eighty years old when, on the conquest of the land, he received his portion at the hands of Joshua. Therefore, forty-five years elapsed since the former date, of which forty, or thirty-eight, had been spent wandering in the wilderness. The campaigns of Joshua must therefore have occupied at least five or seven years for their accomplishment.
For divers years together, five or six at least, God would have the land to be conquered gradually, for many weighty reasons. The sudden extermination of those nations should have made a part of the land desert. Thereby, an increase in the number of wild beasts, which is particularly noticeable by Moses. Lest, being done without difficulty, suddenly, it should soon be forgotten and despised. Third, by lengthy exercise, the Israelites might grow skillful in the art of war. Fourth, for the trial and effort of their patience, courage, and trust in God. Fifth, to keep them in awe, chastised by these Canaanites when they forsook God. To oblige them to be more careful to please him. Since they saw they still needed his help and protection against their enemies.
Today, many believers have to battle something in their life, whether it be physically or spiritually. However, our battles could be short-term or long-term. God knows what trials and tribulations we face. We have to prepare to be ready to go through them whether we like it or not.