Deuteronomy 7:3-4 Do not intermarry with them. Do not give your daughters to their sons or take their daughters for your sons, for they will turn your sons away from following me to serve other gods, and the LORD's anger will burn against you and will quickly destroy you.
1 Kings 11:2, 9
They were from nations about which the LORD had told the Israelites,
"You must not intermarry with them, because they will surely turn your
hearts after their gods." Nevertheless, Solomon held fast to them in
love.... verse 9 The LORD became angry with Solomon because his heart had turned away
from the LORD, the God of Israel, who had appeared to him twice.
God uses His middle knowledge to warn people. If you put yourself into a given circumstance, you will do this. God knew what would happen if the Israelites intermarried. He knew what the foreign wives would do and how the Israelites would respond. Sadly, Solomon didn't listen.
On divine determinism, God's foreknowledge is logically "too late" to serve as a warning. All (even the hypothetical - if you intermarry, you will fall away) is determined by God. So 1 Kings 11 turns into "I told you I determined you would fall" as opposed to "I told you you would fall".