Why the Latest ISIS Battlefield Victory Matters

— -- The militant group Islamic State, or ISIS, just achieved what is being called its most significant victory in Iraq in the past year, after militants overtook the city of Ramadi.

More than 500 people were reportedly killed as militants advanced into the capital of Iraq's largest province, but U.S. officials looked to downplay the strategic nature of the victory, calling it a "setback."

Watch the ABC News digital original video above to learn more about the loss of Ramadi and what it means for the fight against ISIS.