He took part in the battles of Yorktown, Williamsburg, Gaines Mill and Malvern Hill before he was reassigned to the office of the Medical Director, Washington, D.C. in October 1862.

On May 13, 1863, Forwood was accompanying acting regimental commander George Henry Cram and two enlisted orderlies from General Buford's headquarters back to their camp when they were captured by a band of Mosby's guerillas.

This was quite an embarrassing incident for Captain Cram, and might be the reason Forwood spent the rest of the month on detached service at the Cavalry Corps' dismount camp near Dumfries, Virginia.

They were able to fight their way back across the Rappahannock, but Forwood received a severe gunshot wound to the chest, ending his field service during the war.

Following his recovery from this wound, Forwood was assigned as the executive officer of Satterlee General Hospital in Philadelphia and served there until April 1864.

His service at Fort Riley was punctuated by several field expeditions of the 2nd Cavalry against hostile Indians along the upper Arkansas River.

He was assigned to Fort Brady until October 1872, but a good part of this period was spent on a leave of absence studying yellow fever at a quarantine station near Philadelphia.

During the next three years, he served as a surgeon and naturalist for the annual military reconnaissance and exploring expeditions ordered by General Philip Sheridan.

He again accompanied the exploring expedition in the summer of 1883, this time in the company of President Chester A. Arthur and Secretary of War Robert T. Lincoln.

Forwood departed the university in the summer of 1898 to establish a large hospital and convalescent camp at Montauk, New York to deal with the huge numbers of sick soldiers returning from Cuba.

In 1901 he was assigned to duty in the office of the Surgeon General in Washington, and that fall was made president of the faculty of the Army Medical School.