“And it will be to them as vain divination in their sight, who have sworn solemn oaths to them (literally ‘oaths of oaths to them'). But he brings iniquity to remembrance that they might be taken.”
The point here would seem to be that the waiters and watchers in Jerusalem would dismiss what was happening as vain divination. They would not be in suspense. They would be confident that they were well able to resist, for they were full of confidence, having sworn solemn oaths with each other, and with others such as Ammon, and were at the ready, and probably because they also counted on a solemn treaty with Egypt for assistance (which came and then melted away).
‘Oath of oaths to them' may possible be alternately translated ‘seven sevens to them', and may indicate that they considered that there was plenty of time until victory was finally ensured at jubile - the fiftieth year. (Compare the seven sevens of Daniel 9:25 where the hope that victory would follow the seven sevens was dashed. Rather there would be seventy sevens).
Their hopes however would be in vain, because God would call to mind their iniquity with the result that only certain judgment awaited. They would be ‘taken', that is defeated, and slain or made captive.