There is so much hype surrounding the ongoing US war against ISIS that it’s easy to forget that just a few years ago, the US administration was largely ambivalent toward the group as a whole, and many people were openly praising the Europeans who went to Syria to fight against Assad as freedom fighters.

The Financial Times is reporting that’s where the cell blamed for both the Brussels and Paris attacks came from, and indeed that many of the attackers themselves went to Syria to join Islamist factions before ISIS had more than a token presence, back when the US involvement in Syria was exclusively backing rebel blocs.

Brussels bomber Najum Laachraoui, who was also accused of involvement in the Paris attacks, went to Syria in February 2013. That’s before ISIS had even taken the city of Raqqa, their current capital, and before they’d declared themselves a caliphate.

He’s not the only one, as Iraqi government adviser Hisham al-Hashimi notes that a lot of the Brussels-Paris cell arrived in Syria and joined the Tariq bin Ziyad battalion in this period, and that their focus at the time was exclusively fighting in Iraq and Syria.

When ISIS gains in Syria started spreading into Iraq, and some major Iraqi cities started falling, the West changed their mind and was suddenly intervening against ISIS. It was at this point that many of the cell members were sent back to Europe to give themselves an operational presence in countries that had joined the US-led anti-ISIS coalition.

It isn’t as though intelligence officials weren’t predicting this problem, but in 2013 policy makers were largely ignoring it, on the grounds that the fighters were necessary for the anti-Assad push. Islamist factions, after all, were the only ones gaining any ground in the civil war.

Western opinion can do a 180 at a moment’s notice though, and that’s what they ultimately did, going to war with ISIS despite ample warning that many ISIS fighters held Western passports, and could easily return to launch attacks. When exactly that happened, officials still acted both surprised, and totally unprepared to cope with ISIS strikes.