Seven Nations War

I should also add - the Israelites did this after the revelation of the Creator of all things and the God of morality (after the event at Mount Sinai), and although today we are not sure of its truth, we do not have the moral right to do so (and a person must look at himself carefully without prejudice). However, how do they know that they were commanded to do so?
Rabbi Moshe Shapira always pointed out that the way to check the source of the decision is by examining the merits. In other words, the fact that in Gaza they rejoice and exult over the blood of a murdered Jewish baby proves that truth and justice are not guiding them.

Not at all similar.
Rambam wrote: No one makes war with a person in the world until they call him peace, one is a war of authority and one is a war of commandment as it is said that if you approach a city to fight against it and call it peace. If they complete and accept the seven commandments that the sons of Noah were commanded to do, they will not kill a soul, and indeed they are for tribute as it is said, They will be for tribute to you and they will serve you

Three writings Joshua sent before he entered the land, the first one sent them, whoever wants to flee will flee and return and send, whoever wants to make peace will make peace and return and send, whoever wants to make war will do

Avner, what you're missing is that Hamas would advertise an option for Israelis to pay taxes and become slaves of the Palestinians, and also give Jews the option to flee the country, and only after the Jews in Israel surprisingly refuse would Hamas have moral permission to massacre?

Another note - the Torah indicates that the entire world heard about God's revelation to the Israelites, so they probably had to accept it, right?

Of course, the question is if you ask Hamas themselves, do they think they are moral? What will they say? To the best of my knowledge, their answer is religious. And then we return to the thorny issue of religion versus morality, and Rabbi Mikhi comes along and says that morality has the same status as (or perhaps more) than religion, and this is why Hamas terrorists are immoral. But the problem is that Hamas terrorists themselves do not think that way (meaning that in their opinion religion precedes morality). And if so, in the end, the reason they are immoral is because they are simply wrong. In any case, all that remains is to ask whether you think the Israelites were wrong or not. (And now Rama will come along and say, "Haven't I already warned you many times that facts should not be confused with values?" And we will say, "We have not been privileged to understand whether this claim itself is a claim of fact or value, and so on.")

Peace and blessings for the fruitful discussion,

Here is a quote from a reply that Rabbi Moshe Rat also wrote to me on this matter:
“The reply is very simple. Our ancestors are not like Hamas, who slaughtered innocent people, but like IDF soldiers who went to war against the culture of evil. After all, the people of Canaan were not just innocent people, but a corrupt culture in which they sacrificed masses of babies and children to demons and idols, gave girls to ritual prostitution in temples, and were immersed in all moral abominations. God tells Abraham that only his fourth generation will return to the land, “for the iniquity of the Amorites has not yet been fulfilled”, meaning that only when their iniquities were fulfilled – was destruction decreed upon them. And even when the Israelites arrived in the Land, Joshua sent letters in which he gave everyone the opportunity to reconcile and live in peace, on the condition that they surrender to Israel and accept the Seven Commandments of the Children of Noah. If they had done so, they could have stayed alive. In any case, it is clear why the comparison to Hamas does not begin, and this is without mentioning the torture and cruel abuse of Hamas, which was not among the Israelites”

And regarding the killing of children, he wrote:
“First, one must understand that war is a conflict between nations, between collectives, and not between individuals. In any case, the treatment of anyone who belongs to the enemy nation is not as an individual but as part of the enemy, just as when you fight someone you also harm the parts of their body that do not attack you directly.
Secondly, there is corruption that passes through the genes or souls, and will inevitably also be expressed in the descendants of those nations, such as the peoples of Canaan and Amalek. Therefore, the commandment came to destroy them as well.
Third, technically, it is not possible for babies and children to survive on their own, and to impose on the people of Israel the responsibility of raising all the descendants of the Canaanites – This does not make sense, especially since when they grow up and hear what was done to their ancestors, they will probably want revenge. Therefore, it is requested that they be killed.”

Perhaps this is a reasonable answer regarding the Canaanites, but regarding Amalek, there is no answer here unless Rabbi Rat claims that Amalek was also among the Canaanite peoples.
But the bigger problem is the many places in the Bible where immoral warfare is mentioned, for example, in every war that occurs, it is obligatory to kill all the men (not necessarily a war against the Canaanites where every man must be killed), as is written at the end of Parashat Shofitim, and in general in Tractate Berakhot, it is written that the justification for war can be purely economic.

Perhaps the words of the Rambam quoted by Avner above are the answer. It seems that in the Rambam's opinion, in any war, the justification for murder is if the people do not accept upon themselves the Seven Commandments of the Children of Noah.