Short answers, pulled from the story.
Mary of Burgundy wed Archduke Maximilian of Austria in 1477, transferring the Burgundian Netherlands to the House of Habsburg. This marriage bound seventeen distinct territories into a single entity under Habsburg control.
Charles V completed the unification of the Seventeen Provinces with the conquest of the Duchy of Guelders in 1543. He was the first ruler to bring all seventeen provinces under his direct control.
The Pragmatic Sanction of 1549 declared the provinces an indivisible whole to prevent their fragmentation after Charles V's death. This legal instrument legally bound the seventeen provinces to be inherited by one monarch.
The Eighty Years War began in 1568 as a struggle for autonomy against Philip II of Spain. The conflict arose from Philip's centralizing policies, insistence on religious uniformity, and the distance between the Spanish court and the Low Countries.
The Fall of Antwerp occurred in 1584, causing a massive exodus of skilled workers and merchants from the south to the north. This event shifted the economic center of the Low Countries from southern cities like Antwerp to northern cities such as Amsterdam, The Hague, and Rotterdam.
The Treaty of Westphalia formalized the independence of the Dutch Republic in 1648. This treaty divided the Low Countries into the independent Dutch Republic and the southern provinces that eventually became part of modern Belgium and Luxembourg.