The Battle of Al Kasr al Kebir, fought between Moroccan forces and the Portuguese army, marked a pivotal confrontation in the struggle for control in North Africa. The confrontation was part of a larger campaign by King Sebastian of Portugal, who sought to expand Portuguese influence in the region. The battle took place in August 1578, as Sebastian gathered a substantial force that included Portuguese nobles and mercenaries, eager for glory and territorial gains. The Moroccan forces, led by Sultan Abd al-Malik, utilized their knowledge of the terrain and mobilized their troops effectively against the invaders.

Despite being well-equipped and having superior numbers, the Portuguese faced fierce resistance. The battle culminated in a disastrous defeat for King Sebastian, who was killed, leading to a power vacuum in Portuguese leadership. The loss was not merely a military setback but also precipitated a major political crisis back in Portugal, as King Sebastian's death ended the Avis dynasty and left Cardinal Henry, his uncle, as the reluctant successor. The crisis would unfold as various factions vied for power, leading to a period of instability for Portugal.

In the aftermath, the implications of the battle extended beyond the immediate context. The Moroccan victory symbolized the waning influence of Portugal in North Africa and the rise of indigenous power. Additionally, the battle's outcome set the stage for subsequent events leading into the Iberian Union, which saw Portugal united with Spain under a single crown, further affecting the geopolitics of the region for decades to come. This battle would later be cited as a significant turning point in both Portuguese and Moroccan histories, shaping their respective futures.