The background of the Hebrews’ link with Canaan (later the land “Israel”) (the inhabitants of Canaan sacrificed their children in the fire, see below) is this: Abram (later “Abraham”) moves with his father, his wife (Sarai, later “Sarah”) and his nephew (Lot) (among others) from Ur in Mesopotamia to Haran (in the settled world of the post-Babel nations, in what is now Iraq). In Haran God gives Abram “The Promise(s)” if he will go with God to “the land which I will show you.” This land is Canaan, which is why it is also called the Promised Land. However, because of a famine, Abram first goes to Egypt (precursor to what would happen later). Isaac is born in Canaan, and Jacob (later “Israel”) is born to Isaac. Jacob flees Canaan out of fear for his brother Esau (back into to what is now Iraq), then flees back to Canaan out of fear for his father-in-law, Laban (Jacob and Esau make amends). Joseph, Judah, and the other ten brothers are born to Jacob in various places amidst all this back-and-forth, all twelve brothers composing the heads of the twelve tribes of Israel. Eleven of the brothers (although Reuben is not all for it, but keeps the secret) sell Joseph into slavery out of jealousy, and he winds up in Egypt. Joseph gains Pharaoh’s favor by interpreting his dream when no one else could, and Pharaoh makes him governor. The dream he interpreted predicted famine, which allows preparation for it as governor, so his brothers in Canaan have to request grain from Joseph in Egypt during the famine (so widespread it affects both Egypt and Canaan). Because Joseph forgives his brothers, the whole family moves down to Egypt and the Israelites prosper and multiply until a new Pharaoh is in power (200 years after Joseph’s death) who enslaves the Israelites and attempts to decrease their numbers by having their midwives kill their babies. Moses escapes this as a baby and grows up to be used by God to free the enslaved Israelites from Egypt to the Promised Land.

The Israelites are told before even entering the Promised Land to “utterly destroy” the inhabitants of the land so that they could not teach the Israelites to worship other gods (Ex 23:20-33; Deut 7:1-11; 20:17-18). Why? —

Take a moment to recall that when God promised Abram a son in Abram and Sarai’s old age, at the same time He told him his offspring from this son would return to Canaan four generations (400 years) later (after their slavery in a land that is not theirs), when the iniquity of the Amorite is complete (Gen 15:13-21). The Zondervan NASB study note on Genesis 15:16 reads, “Just how sinful many Canaanite religious practices were is now known from archaeological artifacts from their own epic literature, discovered at Ras Shamra (ancient Ugarit) on the north Syrian coast beginning in 1929. Their ‘worship’ was polytheistic and included child sacrifice, idolatry, religious prostitution and divination (cf. Deut 18:9-12). God was patient in judgment, even with the wicked Canaanites.” To answer your question more directly, Navigator – “Are you actually defending slaughtering people because they refuse to follow the true God?” — The Canaanites serve as an example of what man is capable of, and how God deals with him, when he separates himself from God and goes his own way. When the Israelites arrive to the land God has promised them, the Canaanites are ripe for judgment, and the Israelites are the people God uses to bring about that judgment. The Canaanites are the bad guy in the movie – the one who does all sorts of evil unchecked. The Israelites are the hero in the movie – the one who attempts to put an end to the bad guy, even though it means risking death and becoming like the bad guy as long as he’s still around to influence the hero… so that nobody has to worry about the bad guy terrorizing them anymore. Some may feel sorry for the bad guy and wonder if he could have been reformed. Others point out that it is an insult to the bad guy to assume he didn’t know any better. God is patient with the bad guy, though He is saddened and angered by the choices he’s made. But those who trust the hero’s God, trust Him with the bad guy, too. The only people who hate the hero, are the people who relate more with the bad guy, and want to go their own way – which ends in death, hate, and deception. God’s way is life, love, and truth, and this is seen in His judgment of the Canaanites (and Israel).

Because the Israelites do not trust God when He tells them to enter and take possession of the hill country of the Amorites, God makes them wander around in the desert for 40 years to teach them to trust Him (He supplies their food and water, and directs them in where to go by cloud and fire), until all the generation who did not trust God (though they experienced the miracles of The Exodus from Egypt) have died, and only their offspring are left to enter the Promised Land. Taking over where their parents left off, the Israelites’ first battle is with the king of Arad (Canaanite) – a battle their parents had lost a generation before, because they did not fight in God’s timing (at His commission) – Arad provokes the battle. The next two victories, also provoked, are against Sihon (king of the Amorites) and Og (king of Bashan), both of whom are instigators after Israel requests the freedom to pass through the land of the Amorites. They haven’t even fully entered the land and the Israelites are already engaging in the fertility rites of Baal of Peor and are held accountable (Numb 25:1-9), going on to destroy the Midianites who “caused the sons of Israel, through the counsel of Balaam, to trespass against the Lord” (Numb 31:1-18). Moses dies and Joshua takes over (by God’s appointment… also note that every victory is owed to God, and every loss is owed to going their own way). The Israelites take Jericho… and by the end of the conquest it is clear they have not completely rid the land of its inhabitants, ushering in the time of the judges who are necessary to deliver Israel from those they left alive during the Conquest. What is more, once the generation of the Conquest dies, their offspring succumb to Canaanite influence, worshipping the gods (Baals) of the people of the land. Eventually this leads to their exile from the Promised Land (but they are restored… and there’s lots, lots more to the story, which is still in progress as we speak).

For more information on who was sacrificing their children (atleast sometimes by making them pass through the fire, which was one method of sacrifice), and to whom (and where the one true and loving God stood on this) see: Lev 20:1-5; 18:21; Deut 12:29-31; 18:10; 1 Kin 11:5,7; 16:31-33; 21:26; 2 Kin 3:26-27; 16:3 (same as 2 Chr 28:2-3); 17:17; 21:6; 23:10 (Jer 19:5-15); 2 Chr 33:6; Jer 7:31-32; 32:35. These verses as a source are unbiased, because some of them are self-incriminating. Don’t forget earlier reference the artifacts found at Ras Shamra (“against gods” post). To remember that the names of the gods mentioned are interchangeable with other gods, see “against gods” post. See note on Judg 10:6 and 16:23 as to the Philistines. This page offers a good answer as to the Amalekites: http://www.christian-thinktank.com/qamorite.html There’s much more than the quote provides. I haven’t been able to read the whole page yet, as I just found it, but I trust this site in general:

The Amalekite initiative looks like an ordered annihilation.
This is what the LORD Almighty says: `I will punish the Amalekites for what they did to Israel when they waylaid them as they came up from Egypt. 3 Now go, attack the Amalekites and totally destroy everything that belongs to them. Do not spare them; put to death men and women, children and infants, cattle and sheep, camels and donkeys.'” (I Sam 15.2f)
The situation is thus:
1. The Amalekites are a predatory, raiding, and nomadic group; and are descendants of Esau (and hence, distant cousins to Israel).
2. They would have been aware of the promise of the Land TO Israel, from the early promises to Esau’s twin Jacob.
3. They did NOT live in Canaan (but in the lower, desert part of the Negev–a region south of where Judah will eventually settle), and would NOT have been threatened by Israel–had they believed the promises of God.
4. As soon as Israel escapes Egypt–before they can even ‘catch their breath’–the Amalekites make a long journey south(!) and attack Israel.
5. Their first targets were the helpless:
Remember what the Amalekites did to you along the way when you came out of Egypt. 18 When you were weary and worn out, they met you on your journey and cut off all who were lagging behind; they had no fear of God. 19 When the LORD your God gives you rest from all the enemies around you in the land he is giving you to possess as an inheritance, you shall blot out the memory of Amalek from under heaven. Do not forget! (Deut 25.17-19).
6. Before the attack on Amalek is initiated by Israel, the innocent are told to ‘move away’ from them: Saul went to the city of Amalek and set an ambush in the ravine. 6 Then he said to the Kenites, “Go away, leave the Amalekites so that I do not destroy you along with them; for you showed kindness to all the Israelites when they came up out of Egypt.” So the Kenites moved away from the Amalekites. (I Sam 15.5f). This action would have also served to give the people of Amalek plenty of notice (i.e., time to ‘move away’ themselves), and the impending attack by Saul–especially with the troop counts reported!–would hardly have been a surprise. Some of them would likely have fled–we KNOW all of them were not killed, since they ‘lived to fight/raid again’ in David’s time (I Sam 27,30) and even in Hezekiah’s time (200-300 years later!, 1 Chr 4.43).
Kaiser notes in EBC: Exodus 17.8:
Amalek’s assault on Israel drew the anger of God on two counts: (1) they failed to recognize the hand and plan of God in Israel’s life and destiny (even the farther-removed Canaanites of Jericho had been given plenty to think about when they heard about the Exodus–Josh 2.10); and (2) the first targets of their warfare were the sick, aged, and tired of Israel who lagged behind the line of march (Deut 25:17-19).
But Amalek continues to repeatedly oppress, terrorize, and vandalize Israel for between 200 and 400 more years! And yet, Amalekites were freely accepted as immigrants to Israel during this period.
Let’s note again that (1) they had plenty of access to ‘truth’ (at LEAST 400 years since Jacob and Land-promise), plus enough information about the miraculous Exodus to know where/when to attack Israel; (2) even their war conduct was cruel by current standards(!); (3) the semi-annihilation was a judgment; (4) God was willing to spare the innocent people–and specifically gave them the opportunity to move away; (5) children living in the households of stubbornly-hostile parents (who refused to flee or join Israel earlier) died swiftly in the one-day event (instead of being killed–as homeless orphans–by a combination of starvation, wild beasts, exposure, disease, and other raiders; or instead of being captured and sold as foreign slaves by neighboring tribes, for the older ones perhaps?)–they are victims of their fathers’ terrorist and oppressive habits toward Israel; (6) the innocent members of the community (Kenites) and any change-of-heart Amalekites who fled are delivered (along with their children of the household).
[This brief summary above was objected to by a passionate writer, who asked Shouldn’t the butchering of Amalekite children be considered war crimes? (Feb 19/2000, Part one:159k), and centers mostly on the emotionally difficult problem of the killing of the children (of Amalekites, but it would extend generally to the Canaanites and others as well).]

http://www.christian-thinktank.com/qamorite.html

The Conquest and the Ethical Question of War

Many readers of Joshua (and other OT books) are deeply troubled by the role that warfare plays in this account of God’s dealings with His people. Not a few relieve their ethical scruples by ascribing the author’s perspective to a pre-Christian (and sub-Christian) stage of moral development that the Christian, in the light of Christ’s teaching, must repudiate and transcend. Hence the main thread of the narrative line of Joshua is an offense to them.

It must be remembered, however, that the book of Joshua does not address itself to the abstract ethical question of war as a means for gaining human ends. It can only be understood in the context of the history of redemption unfolding in the Pentateuch, with its interplay of divine grace and judgment. Of that story it is the direct continuations.

Joshua is not an epic account of Israel’s heroic generation or the story of Israel’s conquest of Canaan with the aid of her national deity. It is rather the story of how God, to whom the whole world belongs, at one stage in the history of redemption reconquered a portion of the earth from the powers of this world that had claimed it for themselves, defending their claims by force of arms and reliance on their false gods. It tells how God commissioned His people, under His servant Joshua, to take Canaan in His name out of the hands of the idolatrous and dissolute Canaanites (whose measure of sin was now full; see Gen 15:16). It tells how He aided them in that enterprise and gave them conditional tenancy in His land in fulfillment of the ancient pledge.

Joshua is the story of the kingdom of God breaking into the world of nations at a time when national and political entities were viewed as the creation of the gods and living proofs of their power. Thus the Lord’s triumph over the Canaanites testified to the world that the God of Israel is the one true and living God, whose claim on the world is absolute. It was also the warming to the nations that the irresistible advance of the kingdom of God would ultimately disinherit all those who opposed it, giving place in the earth only to those who acknowledge and serve the Lord. At once an act of redemption and of judgment, it gave notice of the outcome of history and anticipated the eschatological destiny of mankind and the creation.

The battles for Canaan were therefore the Lord’s war, undertaken at a particular time in the program of redemption. God gave His people under Joshua no commission or license to conquer the world with the sword but a particular, limited mission. The conquered land itself would not become Israel’s national possession by right of conquest, but it belonged to the Lord. So the land had to be cleansed of all remnants of paganism. Its people and their wealth were not for Israel to seize as the booty of war from which to enrich themselves (as Achan tried to do, ch. 7) but were placed under God’s ban (were to be devoted to God to dispense with as He pleased). On that land Israel was to establish a commonwealth faithful to the righteous rule of God and thus be a witness (and a blessing) to the nations. If she herself became unfaithful and conformed to Canaanite culture and practice, she would in turn lose her place in the Lord’s land—as she almost did in the days of the judges, and as she eventually did in the exile.

War is a terrible curse that the human race brings on itself as it seeks to possess the earth by its own unrighteous ways. But it pales before the curse that awaits all those who do not heed God’s testimony to Himself or His warnings—those who oppose the rule of God and reject His offer of grace. The God of the second Joshua (Jesus) is the God of the first Joshua also. Although now for a time He reaches out to the whole world with the gospel (and commissions His people urgently to carry His offer of peace to all nations), the sword of His judgment waits in the wings—and His second Joshua will wield it (Rev 19:11-16).

– p. 271 essay preceding book of Joshua in Zondervan’s NASB Study Bible, 1999.