Abstract: A compressor section of a gas turbine engine includes an upstream portion and a downstream portion. The upstream portion includes at least one stage of stator vanes and at least one stage of blades configured to rotate about an axial centerline of the compressor section. The at least one stage of stator vanes and the at least one stage of blades are in an alternating arrangement along an axial direction of the gas turbine engine. The downstream portion is disposed immediately adjacent to and downstream along the axial direction from the upstream portion. The downstream portion includes a first set of rotating blade rows and a second set of rotating blade rows. The first and second sets of rotating blade rows are in an alternating arrangement along the axial direction of the gas turbine engine. The first and second sets of rotating blade rows are in a counter-rotating arrangement.