Some people draw a careless assumption from a surface evaluation of Exodus 23:20-33, leading to a shallow conclusion: that if the Israelites had just obeyed God, they would have marched into the land and taken it over without a fight. Such submission would have undoubtedly made their course easier and produced better results.
However, many other contexts show that God tests His people because He is preparing them for future responsibilities. Israel failed many tests. The march through the wilderness and the conquest of the Promised Land was a school, a vast, almost fifty-years-long training ground, for appreciating, using, and governing the Promised Land. This "schooling" included tests by which the Israelites could measure their progress, and at the same time, prove to God their growth and readiness.
We concluded that God's promises in Exodus 23 were indeed conditional. Their fulfillment depended on Israel's obedience, and part of that obedience was confronting their enemies, the people of the land, in warfare. The episode recorded in Numbers 13-14 reveals that the Israelite spies fully expected to have to fight the Canaanites, Hittites, Jebusites, etc. They did not understand Exodus 23 as a free pass, as many do today. Their responsibility was to drive them out in cooperation with God, as He promised to be with them, enabling them to drive the people out, which they were incapable of doing without His involvement. But they refused to do their part.
They were to drive out the inhabitants even as we, in cooperation with God, are to confront and drive out old habits, attitudes, and loyalties. These are negative characteristics left over from our pre-conversion days. Christian living parallels this Old Testament instruction. This is one reason why the New Testament has so many illustrations and exhortations regarding Christian warfare.
Our warfare is in many ways different. It does not involve bloody engagements featuring swords, spears, or rifles with bayonets. It is a spiritual warfare, one that takes place primarily within ourselves. Nonetheless, it requires qualities such as loyalty, patriotism, courage, self-denial, vision, understanding, and sacrifice for us to be victorious overcomers.