In October 1775, he obtained a commission as major and aide-de-camp to General George Washington. After less than a month, he was dismissed by Washington for not being ready enough with his pen and being unsuited for clerical work. On February 9, 1776, White was commissioned by the Continental Congress as the lieutenant colonel of the 3rd New Jersey Regiment. He fought at the Battle of Monmouth, with his dragoons taking the lead as the most advanced scouting parties in the morning offensive.

On May 6, 1780, with the remnant of Major Benjamin Huger's cavalry, he crossed the Santee River and captured a small party of British, but while waiting at Lanneau's Ferry to recross the river, he was surprised and defeated by Col. Banastre Tarleton. White and many of his troops were taken prisoner. In 1781 he was ordered to join the army under Lafayette in Virginia, and on his march to that state had several successful encounters with Colonel Tarleton.