After the couple fled Boston in 1775, she remained essentially homeless until the British evacuated the city in March 1776. Even afterward, she often traveled to visit Knox in the field. Her parents left, never to return, with the British during their withdrawal from Boston after the Continental Army fortified Dorchester Heights, a success that hinged upon Knox's Ticonderoga expedition. When the war broke out with the Battles of Lexington and Concord on April 19, 1775, Knox and Lucy snuck out of Boston, and Knox joined the militia army besieging the city. His abandoned bookshop was looted and all of its stock destroyed or stolen. He served under General Artemas Ward, putting his acquired engineering skills to use developing fortifications around the city. He directed rebel cannon fire at the Battle of Bunker Hill. When General George Washington arrived in July 1775 to take command of the army, he was impressed by the work Knox had done. The two also immediately developed a liking for one another, and Knox began to interact regularly with Washington and the other generals of the developing Continental Army. Knox did not have a commission in the army, but John Adams in particular worked in the Second Continental Congress to acquire for him a commission as colonel of the army's artillery regiment. Knox bolstered his own case by writing to Adams that Richard Gridley, the older leader of the artillery under Ward, was disliked by his men and in poor health. As the siege wore on, the idea arose that cannon recently captured at the fall of forts Ticonderoga and Crown Point in upstate New York could have a decisive impact on its outcome. Knox is generally credited with suggesting the prospect to Washington, who thereupon put him in charge of an expedition to retrieve them even though Knox's commission had not yet arrived. Reaching Ticonderoga on December 5, Knox commenced what came to be known as the noble train of artillery, hauling by ox-drawn sled 60 tons of cannon and other armaments across some of ice-covered rivers and snow-draped Berkshire Mountains to the Boston siege camps. The region was lightly populated and Knox had to overcome difficulties hiring personnel and draft animals. On several occasions cannon crashed through the ice on river crossings, but the detail's men were always able to recover them. In the end, what Knox had expected to take just two weeks actually took more than six, and he was finally able to report the arrival of the weapons train to Washington on January 27, 1776. Called by historian Victor Brooks "one of the most stupendous feats of logistics" of the entire war, Knox's effort is commemorated by a series of plaques marking the Henry Knox Trail in New York and Massachusetts.