Glenn Greenwald explains.

Let’s review Manning’s detention over the last nine straight months: 23-hour/day solitary confinement; barred even from exercising in his cell; one hour total outside his cell per day where he’s allowed to walk around in circles in a room alone while shackled, and is returned to his cell the minute he stops walking; forced to respond to guards’ inquiries literally every 5 minutes, all day, everyday; and awakened at night each time he is curled up in the corner of his bed or otherwise outside the guards’ full view. Is there anyone who doubts that these measures — and especially this prolonged forced nudity — are punitive and designed to further erode his mental health, physical health and will? As The Guardian reported last year, forced nudity is almost certainly a breach of the Geneva Conventions; the Conventions do not technically apply to Manning, as he is not a prisoner of war, but they certainly establish the minimal protections to which all detainees — let alone citizens convicted of nothing — are entitled.