Letters, journals, and reports of the time suggest that, while the service was indeed purchased by various powers, the men that made up the bulk of the Hessian forces had been taken by force of arms, not unlike (although significantly more extreme) than the British Navy. Like the Continental Army and various French and British forces, the official penalty for desertion was death, but unlike those other armies, most of the men were not there by choice, so they dealt more commonly and more severely with desertion, mutiny, and insubordination.

During the battle of Trenton, the majority of the Hessian officers took up with their artillery battery, which commanded much of the area. The necessity of silencing these guns led the Americans to bombard them with their own numerically superior cannon, leading to a slaughter of the Hessian middle-command, the dispersion of their regular infantry, and the general confusion. Rall, the surviving colonel, directed his men to recapture the guns, but the success was short-lived (we're talking minutes) and he himself was laid low in what accounts suggest was a strange mix of bayonet, unarmed combat, and defensive fire (it's worth noting that neither army was able to make optimal use of their firearms due to the weather conditions leading up to the battle, dramatically decreasing the effectiveness of the German Jaegers and Chasseurs as well as Greene's marksmen - a thing which turned out fortunate, in that it rendered both forces much less lethal, except where cannon was involved).

No longer in proper formation and without the influence of their officers, the supposedly strictly-disciplined and bloodthirsty mercenaries were very quick to break ranks, flee (or rather, attempt to), and for the most part surrender. They proved to be easy prisoners, much more keen on farming and the prospect of land-ownership than starting trouble, especially in PA+NJ which had large German-speaking populations to begin with. The overall tone they presented after the defeat was one of good-riddance.