The Three Leagues is the alliance of…

General Howe had proposed to George Germain, the British civilian official responsible for conduct of the war, an expedition for 1777 to capture Philadelphia, the seat of the rebellious Second Continental Congress.

Germain has approved his plan, although with fewer troops than Howe had requested.

He also approves plans by John Burgoyne for an expedition to "force his way to Albany" from Montreal.

Germain's approval of Howe's expedition includes the expectation that Howe will be able to assist Burgoyne, effecting a junction at Albany between the forces of Burgoyne and troops that Howe will send north from New York City.

Howe decides by early April against taking his army overland to Philadelphia through New Jersey, as this would entail a difficult crossing of the broad Delaware River under hostile conditions, and it would likely require the transportation or construction of the necessary watercraft.

Howe's plan, sent to Germain on April 2, also effectively isolates Burgoyne from any possibility of significant support, since Howe will be taking his army by sea to Philadelphia, and the New York garrison will be too small for any significant offensive operations up the Hudson River to assist Burgoyne.

American militia companies, sometimes with Continental Army support, have continued to harass British and German outposts and ambush their foraging and raiding expeditions.

One of the forward bases used for the operations is at Bound Brook, located on the Raritan River upriver from New Brunswick, the major British camp in New Jersey.

The post is responsible for patrolling three bridges across the Raritan likely to be used by the British in moves against the main camp at Morristown.
 
In February 1777, the Bound Brook outpost had consisted of one thousand men under the command of Major General Benjamin Lincoln, but this had been reduced by expiring militia enlistments to five hundred in mid-March.

The troops that remain are from the 8th Pennsylvania Regiment, a company from the 4th Continental Artillery, and two independent companies from the Wyoming Valley in what is now northeastern Pennsylvania, but is at this time also claimed by Connecticut as Westmoreland County.

Lincoln expresses concern over his exposed position to General Washington, noting that many units are not in a position to "render the least assistance to this post in case it is attacked", and that he is keeping wagons ready in case a precipitate departure was needed.

Lieutenant General Lord Charles Cornwallis, in command of the British forces in New Jersey, has had enough of the ongoing petite guerre, and organizes a reprisal action against the Bound Brook outpost.

According to the Hessian jäger Captain Johann Ewald, Cornwallis had asked him to draft a plan of attack in February, but the plan cannot be executed until springtime because it necessitates fording the Raritan.

On the night of April 12, the plan is put into action.

Four thousand British and Hessian troops under the overall command of Cornwallis march from New Brunswick to make a multi-pronged surprise attack.

The right flank, under the command of Major General James Grant, consists of the Hessian jäger corps, grenadiers from the English Brigade of Guards, and a detachment of British light dragoons.

While most of this column advances from Raritan Landing (opposite New Brunswick on the left, or Bound Brook side, of the river), two companies of light infantry go further right, aiming to cut off the main road from Bound Brook to the Continental Army camp at Morristown.

The center, under the command of Hessian Colonel Carl von Donop, consists of the Hessian grenadier battalions von Linsing and Minnigerode, and the left, commanded by Cornwallis, consists of two battalions of British light infantry, the 1st battalion of grenadiers, and another detachment of light dragoons.

Donop's column advances up the right bank of the Raritan, aiming to gain control of the bridge directly at Bound Brook, while Cornwallis takes a longer route to ford the river above Bound Brook and thus cut off the possibility of retreat in that direction.

Johann von Ewald and a few of his jägers are in the vanguard of Grant's column and engage the American sentries to the south of Bound Brook.

Unaware that this is supposed to be a feint, Ewald drives the sentries back nearly to the main redoubt where the outpost's cannons are located.

By sunrise he is nearly surrounded; the timely arrival of von Donop's column just over the river, and the attack by Cornwallis's column prompts the Americans to begin abandoning the post.

The surprise is very nearly complete; the Pennsylvania artillery company, which had been manning the redoubt, is severely mauled, with numerous killed and captured.

Colonel von Donop reports that General Lincoln "must have retired en Profond Négligé" ("profoundly undressed", or naked), and Lincoln's papers are taken.

The British plan is marred by the early skirmishing involving Ewald, and the too-late arrival of the companies sent to cut off the road to Morristown; Many Americans escape via this route.

The British capture also cannons, ammunition, and supplies, and loot Bound Brook, but return to New Brunswick later in the morning.

The Continental Army response is immediate; Washington sends a large force under Major General Nathanael Greene to reoccupy Bound Brook.

The British have already left by the time they arrive; Greene sends a detachment to harass their rear guard.

This detachment catches up with the British near Raritan Landing, where they kill eight and capture sixteen.

General Howe reports that about thirty Americans have been killed and eighty to ninety have been captured, while General Lincoln reports that sixty of his men have been killed or wounded.

Howe claims no deaths and seven wounded among the British and Hessians.

Washington reports that "[t]he enemy lost the post at Eleven O'Clock the same day, & our people took possession of it again", and that the army's losses were "trifling and not worth mentioning".

He did, however, also report that between thirty-five and forty killed or captured, and the loss of three field cannons.

In a report to the Board of War, Washington admits the capture of two cannons, two officers and twenty men from Colonel Proctor's Regiment.

General Greene reports to his wife, "The British Generals breakfasted and I [dined] at the same house that day".

Washington, concerned that the attack presages an early start to the campaign season, worries that his troops are not yet in place to deal with major British movements.

Two weeks later, after no further major activity, the Americans learn that "the Enemy are to take the field the first of June."