It was in Union-occupied Alexandria in 1863 that Pvt. Henry Vanderwater, a member of the 1st District of Columbia Volunteers stationed there to defend Washington, got himself in trouble. He gave a military roster to a local newspaper, which promptly printed it. For the offense of aiding the enemy — the roster would indicate how well or poorly the town was protected — he faced a court-martial, was found guilty and received a sentence of three months hard labor and a dishonorable discharge.

Vanderwater’s court-martial would have remained a minor and forgotten piece of history if prosecutors in the court-martial of Pfc. Bradley Manning hadn’t cited the case during pre-trial hearings this past week. Manning is charged with indirectly aiding the enemy. While on active duty in Baghdad, he allegedly sent thousands of military records to the whistle-blowing Web site WikiLeaks, which then published them, giving the world, including al-Qaeda, access to the material....