By Genevieve Casagrande and Jodi Brignola  (ISW) –Key Takeaway: Russian air operations shifted eastward on January 18-19, targeting ISIS-held terrain in Homs, ar-Raqqa and Deir ez-Zour Provinces following a major attack on Deir ez-Zour City by ISIS. ISIS launched an offensive against regime positions on the northwestern outskirts of Deir ez-Zour on January 17, seizing two villages and several military installations under the cover of a major sandstorm that reportedly grounded both regime and Russian aircraft. Russian warplanes subsequently shifted operations away from opposition-held terrain in Aleppo, Idlib, Hama, Homs, Damascus, and Dera’a Provinces in order to target ISIS-held positions along the Euphrates River north and south of Deir ez-Zour City on January 18. The shift in Russian air operations serves to forestall the immediate defeat of regime forces in Deir ez-Zour City, one of the last remaining regime outposts in Eastern Syria. Russia previously carried out its first humanitarian aid drop in Syria on January 15, claiming to deliver over 22 tons of humanitarian aid to besieged regime positions in Deir ez-Zour City. The aid operation comes amidst renewed diplomatic pressure by the international community to lift sieges on civilian populations in Syria. Local sources could not confirm whether the aid was humanitarian or military supplies.