The goal was “to destroy and lay waste the principal towns and commercial cities assailable either by their land or naval forces.”

From The Battle of New Orleans: Andrew Jackson and America's First Military Victory by Robert V. Remini.  Page 8.

To bring the American nation to heel, the British cabinet worked out a grand plan of conquest. The goal was “to destroy and lay waste the principal towns and commercial cities assailable either by their land or naval forces.” The strategy consisted of a three-pronged invasion from three widely separated areas of the continent: an amphibian thrust into the Chesapeake Bay area aimed at Washington, Baltimore, and other coastal cities; another from Montreal into New York State via Lake Champlain; and a third from the Gulf of Mexico into Louisiana with the purpose of seizing New Orleans and detaching the Mississippi Valley from the Union.

The first part of this grand strategy enjoyed an initial success that further devastated the American people. An amphibian force under Admiral Sir George Cockburn sailed into Chesapeake Bay in August 1814. A crack army of four thousand British soldiers and marines under Major General Robert Ross landed at Benedict, Maryland, and marched on Washington, easily knocking aside a superior number of American militiamen gathered at Bladensburg to block the invasion. President Madison fled to Virginia. His wife, Dolley, managed to make her escape in a wagon filled with “valuable portable articles,” including a large portrait of General Washington that had to be unscrewed from the wall of the presidential mansion.

The British entered the unprotected city on August 24, 1814, and set fire to the Capitol, the White House, and all other public buildings with the exception of the Patent Office. They also burned any private dwelling from which shots were fired at the invaders. But the advance to Baltimore on September 13 was repulsed by thirteen thousand Americans, who had fortified the heights around the city. A British fleet tried to bombard Fort McHenry into submission, and when the attempt failed the invaders withdrew.

At approximately the same time that Ross and his men advanced on Baltimore, a red-coated army of ten thousand veterans, commanded by General Sir George Prevost, crossed the Canadian border and arrived at Plattsburg, New York, on September 6, 1814. Before continuing his advance, Prevost decided to wait until a British fleet could enter Plattsburg Bay and assist him in storming the American position. But Lieutenant Thomas Macdonough of the U.S. Navy and his squadron outfought the superior British fleet and prevented it from entering the bay, thereby retaining control of the strategic Lake Champlain. Without that naval assistance and unable to proceed further, General Prevost turned around and retreated back to Canada.