The last decades have been marked by a high competitive intensity and a strong turbulence of the environment. Passive strategies that are based on the structuralist model are no longer reliable in a dynamic environment where it becomes difficult to maintain a sustainable competitive advantage. Hence, what models and strategic choices were adopted by companies as regards with these environmental changes? Through the study of the case of the Tunisian Chemical Group (GCT), our research aims to understand the strategic behavior of a large firm in a turbulent environment and in a sector with strong rivalry. Our research is based on the case study method which is the most frequently used in previous works dealing with the complex issues such as a competitive dynamics field. The primary finding argue the idea of polyvalent strategy inspired by the behavioral model which consists in alternating two logics often considered as antagonistic: market fit and strategic intent. We believe that firms tend, within the framework of a dual strategic flexibility, to combine contradictory competitive advantages and different strategic postures.