He interrupted his studies and fought in the War of 1812, serving with his brother Samuel.

He saw action at Chippewa, Lundy's Lane, Buffalo, and Fort Erie, and was noted for his bravery.

[1] After the war, he completed his legal education and then started practicing in Juniata County.

During this term, he was appointed state Attorney General, to fulfill the vacancy formed when the incumbent accepted a judgeship, but he served only three months.

[3] In 1832, the newly founded Pennsylvania College of Gettysburg appointed Blythe to their Board of Trustees, which he served on until 1844.