In response to the request of the Continental Congress, the Lower Counties Assembly raised the 1st Delaware Regiment, placing John Haslet at its command on January 19, 1776, with the rank of colonel.

At the Battle of Long Island, the Delaware Regiment fought with Colonel William Smallwood's Marylanders. Many thought these were the two best regiments in the Continental Army. They fought under the command of Brigadier General William Alexander, Lord Stirling, and were responsible for holding the Gowanus Road, the far right of the Continental Army line. They were immediately south of Brooklyn, with New York Harbor to their right. On August 27, 1776, the British sent much of their army well to the east, and under cover of darkness, easily turned the left flank of the Continental Army. Only on the right did the American's hold their own. McCullough again relates how Haslet later described "how his 'Delawares' stood with 'determined countenance', on them all the while, and the enemy, 'though six times their number', not daring to attack". But they were nearly surrounded and, once ordered to leave, could only undertake a harrowing retreat by wading and swimming across Gowanus Bay. When the fighting began, Haslet was attending a court martial in Manhattan, but returned to the regiment in time for some of the fighting.

Retreating across Westchester County, Haslet's men won a victory over a corps of Loyalists at Mamaroneck, New York. At White Plains, on October 28, 1776, the Delaware Regiment again fought with Colonel William Smallwood's Marylanders, reinforcing militia placed on the strategic Chatterton's Hill. The local militia fled under the British attack, but Haslet and Smallwood fought on until, at last, they too yielded the ground. The Battle of White Plains was another British victory, but because of the difficulty in taking Chatterton's Hill, the price was great and the reward to the British was little.

With expiring enlistments leaving fewer than 100 men remaining in his regiment, Haslet crossed the Delaware with Washington and joined the attack at the Battle of Trenton on the morning of December 26, 1776. However, on January 3, 1777, in a skirmish at the beginning of the Battle of Princeton, with General Hugh Mercer down and wounded, Haslet tried to rally Mercer's brigade and was himself shot in the head and killed instantly. Nevertheless, they did rally and a surprising victory was won to complement the earlier one at Trenton. The "corps of loyalists" he defeated at Mamaroneck was led by the famous Indian fighter Robert Rogers (soldier). Legend has it that Washington wept over his corpse on the battlefield and notes by Washington's stepson confirm that Washington did come across Haslet's body at Princeton, but does not mention any shedding of tears.

Link to wiki about the colonel: https://en.wikipedia.org/wiki/John_Haslet Link to painting: https://upload.wikimedia.org/wikipedia/commons/b/b3/BattleofLongisland.jpg