What was passing at Brunswick has fortunately found a record in the diary of a British officer posted there when the news of Washington's coming fell like a bombshell in their camp. It is given word for word:
On the 3d we had repeated accounts that Washington had not only taken Princeton, but was in full march upon Brunswick. General Matthew (commanding at Brunswick) now determined to return to the Raritan landing-place, with everything valuable, to prevent the rebels from destroying the bridge there. We accordingly marched back to the bridge, one-half on one side, the remainder on the other, for its defence, never taking off our accoutrements that night.
On the 3d, Lord Cornwallis, hearing the fate of Princeton, returned to it with his whole force, but found the rebels had abandoned it, upon which he immediately marched back to Brunswick, arriving at break of day on the 4th. I then received orders to return to Sparkstown (Rahway?). Washington marched his army to Morristown and Springfield. At about the time I arrived at Sparkstown, a report was spread that the rebels had some designs upon Elizabethtown and Sparkstown. The whole regiment was jaded to death. Unpleasant this! Before day notice was brought to me by a patrol that he had heard some firing towards Elizabethtown, about seven miles off. I immediately jumped out of bed and directed my drums to beat to arms, as nothing else would have roused my men, they were so tired. Soon after this an express brought me positive orders to march immediately to Perth Amboy, with all my baggage. At between six and seven the rebels fired at some of my men that were quartered at two miles distance. I had before appointed a subaltern's guard for the protection of my baggage. This duty unluckily fell upon the lieutenant of my company, which left it without an officer, the ensign being sick at New York. I immediately directed my lieutenant, who was a volunteer on this occasion, to march with his guard, that was then formed, to the spot where the firing was, while I made all the haste I could to follow him with the battalion.
The lieutenant came up with them and fired upwards of twelve rounds, when, the rebels perceiving the battalion on the march, ran off as fast as they could. Had I pursued them I should perhaps have given a good account of them.