Positive signs in the fight against Islamic State in Iraq and Syria have recently been tempered by signs that the militant group is making serious inroads in Libya – a theater that will pose a much greater challenge to Western policymakers.

Up until now, Islamic State’s presence in Libya has been small given the chaos reigning in the country. The group took most of Derna, a city along the Mediterranean coast in eastern Libya, back in 2014 after pushing back rival militias loyal to al-Qaeda. Sirte was next to fall after a two-month battle in mid-2015. Since then, ISIS has been pushed out of Derna and has expanded its territory to the east and west of Sirte.

Early gains by Islamic State in Libya came on the back of opportunistic militias which sought the Islamic State ‘brand’ for their own recruitment purposes, rather than any centrally directed effort from the ISIS leadership in Raqqa.

The situation now appears to be changing. As ISIS is pinched between coalition air support and a sustained push from the Iraqi security forces, its manpower is beginning to drain from the Iraq-Syria battlefield. The latest White House estimate puts the group’s strength there at anywhere from 19,000-25,000, down from the earlier count of 20,000-32,000.

The foreign fighters that would normally be bolstering these ranks aren’t heading to Raqqa like they were before. Instead, they’re beginning to flood into Libya, apparently at the behest of an ISIS leadership that sees gains to be made in the anarchy that has set in following Gaddafi’s ouster.

Estimates put Islamic State’s strength in Libya at 5,000 and growing. The group’s territorial footprint is minor, restricted as it is to the areas around Sirte, but we may be seeing a deliberate build-up of manpower ahead of an unexpected blitz much like the strategy employed against Fallujah and Mosul in 2014.