Advanced Tactical Training

From Memory Alpha, the free Star Trek reference.

Advanced Tactical Training is a special course for Starfleet officers. Officers must be recommended for this training. It is very difficult and challenging, in fact, half of the class washed out each year.

Ensign Ro Laren attended Advanced Tactical Training per the recommendation of Captain Picard. After her training, Admiral Nechayev felt that Ro Laren's training qualified her for an infiltration mission of the Maquis. Ro was hesitant and even mentioned that one of her instructors in Tactical Training (a Lieutenant Commander) was sympathetic to the Maquis.

This instructor was intended by the producers to be a reference to Commander Chakotay following the creation of Star Trek: Voyager. Ro's article at StarTrek.com states this as part of her biography.

Ro was later able to use the training to trick the Enterprise and 'steal' supplies from while working undercover with the Maquis (prior to defecting later in the episode). (TNG: "Preemptive Strike")