Isn't God merciful? Why He took so many lives in Old Testament?

Why God let the Israelites to kill many people and take over their land? Isn’t God merciful? Some people say these are holy war, I couldn’t understand clearly.

God is not beholden to us at all. He doesn’t owe us anything.

Now add to that the fact we’re all sinners and deserve to die and go to hell yesterday, and the reality that we’re even breathing today is sheer common grace from God.

…God has his times and seasons for when he shares his authority to take and give life. And the church today is not Israel, and we are not a political entity. Therefore the word we have from the Lord today is, “Love your enemy. Pray for those who abuse you. Lay your life down for the world. Don’t kill in order to spread the gospel, but die to spread it.”

Concerning the Incarnation of Israel into the Land of Canaan, it is God’s intention that Israel, before settling in Canaan, should be sure to completely remove the deteriorating inhabitants of the idols and worship idols of that place.

The reason is to save the people of Israel, so that they may live peacefully in that place, as their ancestors did, testifying to the one true God alone.

Just as a doctor wants to completely rehabilitate a patient who has had a toxic tumor, God has to cut off all the cancers in the patient!

【Gen. 6:5-7】
The Lord saw how great man’s wickedness on the earth had become, and that every inclination of the thoughts of his heart was only evil all the time.
The Lord was grieved that he had made man on the earth, and his heart was filled with pain.
So the Lord said, ‘I will wipe mankind, whom I have created, from the face of the earth-men and animals, and creatures that move along the ground, and birds of the air-for I am grieved that I have made them.’

【Gen. 6:11-13】
Now the earth was corrupt in God’s sight and was full of violence.
God saw how corrupt the earth had become, for all the people on earth had corrupted their ways.
So God said to Noah, 'I am going to put an end to all people, for the earth is filled with violence because of them. I am surely going to destroy both them and the earth.