The capture of the Sơn Tây citadel by French forces marked a pivotal moment in the Tonkin Campaign, part of the broader French colonial ambitions in Vietnam during the late 19th century. Located in the northern part of Vietnam, the citadel was a prominent military stronghold that had been used by local leaders to stage resistance against foreign incursions. In December 1883, the French launched a decisive attack on the citadel, employing superior artillery and military tactics. After several days of combat, the fortress fell into French hands, enabling them to extend their influence over the Red River Delta region.

Leading the French forces was General François de Négrier, who orchestrated the assault with precision. The operation not only showcased the French military dominance but also highlighted the internal divisions and challenges within Vietnamese leadership, with figures like Phan Đình Phùng, who rallied local forces for a counter-offensive, struggling to unify resistance against the well-armed French troops. The siege and subsequent capture were not merely a change of control; they symbolized a broader struggle for sovereignty and the evolving nature of Vietnam’s resistance to colonialism.

The aftermath of the citadel's capture saw a significant shift in the power dynamics of the region. The French used Sơn Tây as a strategic base for further operations aimed at consolidating their power in Tonkin, leading to increased tension with local Vietnamese. This event set the stage for continued conflicts and wars as the Vietnamese population gradually organized itself against foreign rule, paving the way for future uprisings and the long struggle for independence.