When he did call out the militia five days after the violence began, his troops primarily stood as observers and did not actively try to suppress the riots.

In July of that same year, during three days of rioting in Southwark, a largely Catholic neighborhood in South Philadelphia, Cadwalader ordered his troops to fire into the crowd of nativists trying to destroy St. Philip Neri Church.

These actions resulted in concern over the use of the military against civilian populations and led directly to the creation of a much stronger and more professional police force in Philadelphia.

On March 3, 1847, Cadwalader was appointed brigadier general and took command of a brigade of reinforcements being sent to Winfield Scott in central Mexico.

Due to his distinguished military experience, he was appointed major general of Pennsylvania Volunteers by Governor Andrew Curtin in April 1861.

On May 25, federal troops arrested a Maryland planter, John Merryman, who had been recruiting soldiers for the Confederate army and imprisoned him at Fort McHenry, where General Cadwalader had his headquarters.

In April 1865, General Cadwalader helped found the Military Order of the Loyal Legion of the United States (MOLLUS), a quasi-fraternal organization for former Union Army and Navy officers.