How did the Eighty Years' War lead to separate northern and southern Netherlands?

The Eighty Years' War (1568–1648) resulted in the separation of the Netherlands due to diverging political, religious, and economic interests between the northern and southern provinces.12

Initially, the provinces were united in their resistance against Spanish rule, as seen in the 1576 Pacification of Ghent. However, this unity fractured by 1579. The southern provinces, largely agrarian and Roman Catholic, grew wary of the radical Calvinist movement and the dominance of the commercial northern provinces. This led to the formation of the Union of Arras, which reconciled the south with the Spanish crown.12345

In response, the northern provinces and several southern cities formed the Union of Utrecht in 1579 to continue the resistance. This "closer union" became the foundation of the Dutch Republic. The Spanish commander Alessandro Farnese subsequently reconquered the south, effectively ending the unified revolt by 1585. The division was solidified by the Peace of Westphalia in 1648, when Spain formally recognized the independence of the northern United Provinces.45132