How did the birth of Charles the Bald create a succession crisis in Louis I’s empire?

The birth of Charles the Bald created a significant succession crisis because it disrupted the Ordinatio Imperii of 817, a plan Louis I had established to maintain the unity of his empire while providing for his three existing sons.123

Under the original 817 agreement, Louis’s eldest son, Lothar I, was designated as the sole heir to the imperial title, with his brothers Pippin and Louis the German serving as subordinate kings in Aquitaine and Bavaria, respectively. When Louis I remarried Judith of Bavaria and had a fourth son, Charles, he sought to carve out a new kingdom for him.132

This attempt to reallocate territory to include Charles directly conflicted with the interests of his older sons, who viewed the move as a threat to their established inheritances. These divergent interests led to intense civil strife, including major revolts by the older sons against their father in 830 and 833–834, ultimately undermining Louis I’s authority and setting the stage for the eventual partition of the empire.421