The apostle Paul affirms that the God the Israelites of the Old Testament knew—the One they looked to as their "Rock" of strength (see Deuteronomy 32:4 Deuteronomy 32:4He is the Rock, his work is perfect: for all his ways are judgment: a God of truth and without iniquity, just and right is he.
American King James Version×; Psalms 18:2 Psalms 18:2The LORD is my rock, and my fortress, and my deliverer; my God, my strength, in whom I will trust; my buckler, and the horn of my salvation, and my high tower.
American King James Version×)—was the One we know as Jesus Christ. Notice what Paul wrote in 1 Corinthians 10:1-4 1 Corinthians 10:1-4  Moreover, brothers, I would not that you should be ignorant, how that all our fathers were under the cloud, and all passed through the sea;  And were all baptized to Moses in the cloud and in the sea;  And did all eat the same spiritual meat;  And did all drink the same spiritual drink: for they drank of that spiritual Rock that followed them: and that Rock was Christ.
American King James Version×: "All our fathers were under the cloud, all passed through the sea, all were baptized into Moses in the cloud and in the sea, all ate the same spiritual food, and all drank the same spiritual drink. For they drank of that spiritual Rock that followed them, and that Rock was Christ."
Jesus was the One who spoke to Moses and told Him to return to Egypt to bring the Israelites to freedom. Jesus was the LORD (YHWH) who caused the plagues to come on Egypt. He was the God who led the Israelites out of Egypt and through the wanderings for 40 years. He was the Lawgiver who gave the laws to Moses and spoke to Moses on a regular basis. He was the LORD who dealt with Israel throughout their national history.
Yes, astounding as it seems, Jesus Christ is the LORD (YHWH) spoken of so often in the Old Testament.