Christianity believes that there is one God who is the Creator of all things, and who is sovereign over all things. But a religion like this was very rare in the historical period of the Old Testament. Typically each nation had their own national god which dealt exclusively with that nation. When nations would go to war against each other, they saw it as one god warring against another, and the victor would boast that their god had overcome the other nation’s god. That’s what religion was like back then. But the God of the Hebrews wasn’t like that. He was the supreme God who created all things, and who could both establish nations and tear nations down. All nations were under His sovereign rule. And yet many today will try to tell you that Yahweh, the God of the Hebrews, was actually (at least at the start of Hebrew religion), just another tribal deity.
One of the Biblical “evidences” for this is a passage like Deuteronomy 32:8-9...
When the Most High gave to the nations their inheritance, when he divided mankind, he fixed the borders of the peoples according to the number of the sons of God. But the LORD's portion is his people, Jacob his allotted heritage. (Deuteronomy 32:8-9)
Now, before we can discuss this verse, we need to get a handle on some Biblical terminology. The first thing to note is the term "sons of God". This is a reference to angels. Many Bibles translate this as "sons of Israel", but the most reliable manuscripts (eg the Dead Sea Scrolls) say "sons of God", or "angels". The next thing to note is that, traditionally, Bible translators use the word "LORD" in capital letters when translating the name Yahweh, which is often referred to as God's "personal name". And finally, that the name "Jacob" is synonymous with "Israel". With this in mind, we can see how some people want to read this verse. They will see the "Most High" as allocating gods (or "angels") to each of the nations, just as we discussed in the first paragraph; and that Yahweh (“LORD”) is just another one of these angels, distinct from the "Most High", and he happens to get allocated to Israel, making him just another tribal deity in the typical religious world view of the period.
Now, of course, there is an abundance of Biblical Texts which speak of Yahweh as the Creator of all, and sovereign over all, and that certainly uses "Most High" (Elyon) synonymously with "Yahweh". The first chapters of Genesis are sufficient to show this. But that's not really much help to address this issue. You see, the apparent problem here is that the Bible appears to contradict itself. And what proponents of this view would say is that Yahweh is the product of human invention and mythology; that since the time of Moses people's view of Yahweh changed... he started out as a tribal deity fitting the model of religious belief at that time, but later on Israel sort of changed the mythology behind Yahweh. Proponents typically believe in the "documentary hypothesis", which is the idea that the books of Moses (the “Torah”) is actually a compilation of texts written at various times throughout Israel's history, from some unknown point in the past right up to the Babylonian captivity. So that even if Genesis tells us that Yahweh is the Creator, that's just one person's view (not Moses' own view), and the song written in Deuteronomy 32 is some other author's view of Yahweh; presumably a very early one before Israel made Yahweh "God of all".
What this passage in Deuteronomy 32 is really telling us is that God set up all the nations, and He seems to have set an angel over each one, but that God Himself (and not some angel) is over Israel, and has a special relationship with Israel. This idea that angels have been allotted to certain nations may be Biblically supported by a passage such as we find in Daniel 10...
Then he [an angel] said to me, "Fear not, Daniel, for from the first day that you set your heart to understand and humbled yourself before your God, your words have been heard, and I have come because of your words. The prince of the kingdom of Persia withstood me twenty-one days, but Michael, one of the chief princes, came to help me, for I was left there with the kings of Persia, and came to make you understand what is to happen to your people in the latter days. For the vision is for days yet to come." (Daniel 10:12-14)
This certainly seems to refer to angels over nations, since the speaker is an angel and would not be opposed by a human prince. Later, Daniel writes:
At that time shall arise Michael, the great prince who has charge of your people. And there shall be a time of trouble, such as never has been since there was a nation till that time. But at that time your people shall be delivered, everyone whose name shall be found written in the book. (Daniel 12:1)
Daniel certainly sees Yahweh as being the supreme God over all. A central theme in the whole book of Daniel is how God is over all nations to rise and fall as He pleases. There is no doubt in Daniel’s mind as to who is sovereign over all nations (eg Daniel 2:21). And we just saw in Daniel 10:12-14 and 12:1 that Daniel also understands there to be angels given charge over the nations, and he even cites Michael, not Yahweh, as the angel given charge over Israel. Deuteronomy tells us that Israel is “Yahweh’s portion”, and that remains true for Daniel; Michael and these other angels are servants of God; or as the book of Hebrews puts it, “ministering spirits sent out to serve for the sake of those who are to inherit salvation” (Hebrews 1:14).
In a documentary on Biblical archaeology, I once heard an archaeologist point to various stone idols of pagan gods which he’d dug up in Israel, and he said “I hate to tell you folks, but Israel was not a monotheistic culture!” And I was a little dumb-founded... like, “Who on Earth has read the Bible and doesn’t already know that!?” The Bible exposes at great length the idolatry of the people of Israel, and of the neighbouring nations. Furthermore, it goes so far as to say that many of these gods were literal, spiritual beings. For example, the Bible says “So they shall no more sacrifice their sacrifices to goat demons, after whom they whore...” and in the Psalms “They sacrificed their sons and their daughters to the demons” (Psalms 106:37). So Deuteronomy 32 is, in a sense, telling us of a “polytheistic” reality. From a human perspective, angels and demons are gods in so far as we have worshipped them. But from God’s perspective they are no gods at all, as it reads in Deuteronomy 32 itself...
They sacrificed to demons that were no gods... (Deuteronomy 32:17)
My point is this... There are two ways we can take Deuteronomy 32:8-9. In both, God has given angels charge over the nations, and people have worshiped those angels as gods. But in one interpretation, the “Most High” is distinct from Yahweh and Yahweh is just another “tribal deity”. Alternatively, we can take it as referring to Yahweh being synonymous with the Most High God Himself, and having a special relationship with Israel. The interpretation that the rest of the Bible supports unwaveringly is the latter, where Yahweh is synonymous with the Most High, and where the existence of “tribal deities” is acknowledged alongside the absolute supremacy of Yahweh, a supremacy which is never once in doubt. Clearly I think that if you want to believe that the people of Moses’ time saw Yahweh as a tribal deity, it’s because you choose to believe that, since there is nothing Biblically which would compel you towards that view.
I would also be careful of how we take the supposed evidences from other ancient literature which uses terms like “Most High” (Elyon) or “Yahweh” in their religious writings. These arguments can sound very scholarly, but all they really tell me is that God, through Moses, used language to reveal Himself to the people. That is, He used common everyday language which people understood.
Now therefore, if you will indeed obey my voice and keep my covenant, you shall be my treasured possession among all peoples, for all the earth is mine; and you shall be to me a kingdom of priests and a holy nation. (Exodus 19:5-6)