Jamming attacks can severely limit wireless networks availability and can cause serious damage, in particular for tactical applications. Over the past decades, Direct-Sequence Spread Spectrum (DSSS) has been used to enhance resistance to jamming. In this paper, we first analyze the performance of the DSSS modulation in the presence of malicious jamming; we take into account by considering different physical phenomena such as a large Doppler shift and we use at the receiver side robust synchronization algorithms. We then propose to consider jointly rotated constellations and the DSSS technique in order to enhance robustness against jamming, while keeping reasonable complexity. Simulations results underline the good performance of our proposal as it shows a gain of several dBs compared to the DSSS technique with conventional constellations.