The presence of a prograde jet at the equator in a planetary atmosphere is often referred to as super-rotation. On Mars, the strength of the equatorial jet is dynamically coupled to the amount of dust in the atmosphere; strengthening of the equatorial jet by the presence of dust affects dust transport in the tropics, which in turn determines the locations of further dust-driven heating. We used data assimilation to study the interaction between dust and the equatorial jet during the 2018 Mars global dust storm (GDS). The data assimilation scheme integrated temperature and dust information from instruments aboard the Mars Reconnaissance Orbiter and ExoMars Trace Gas Orbiter satellites into a numerical model of the Martian atmosphere, creating a better representation of the atmospheric state than could be achieved from observations or models alone. We found that super-rotation increased by a factor of two at the peak of the GDS, due to enhanced winds in the tropics. A strong westerly jet formed in the tropical lower atmosphere, and easterlies were strengthened above 60 km, as a result of momentum transport by dust-driven thermal tides. We found that the atmosphere was in a state of enhanced super-rotation even before the onset of the GDS, as a result of equatorward advection of dust from the southern mid-latitudes into the tropics. The redistribution of dust across the hemispheres resulted in a more uniform dust distribution across the tropics, leading to a symmetric Hadley cell with a tropical upwelling branch that was closely aligned to the vertical. We argue that the symmetrical circulation and enhanced super-rotation would have been important environmental factors that encouraged the development of the GDS in 2018.