The additional charges leveled at Pfc. Bradley Manning last week provide new information on the timing of Manning’s alleged leaking, including the surprising detail that by the time Manning allegedly leaked a notorious video of a 2007 Army helicopter attack in Iraq, he’d already allegedly passed nearly half-a-million classified documents to WikiLeaks.

The helicopter video, released by WikiLeaks under the title “Collateral Murder” last April, was generally presumed to have been one of Manning’s earliest leaks to the secret-spilling website.

The charge sheet released Tuesday indicates that the...