The painting is renowned for three elements: its colossal size (363 x 437 cm ~ 11ft 10in x 14ft 4in), the effective use of light and shadow, and the perception of motion in what would have been, traditionally, a static military portrait.
This painting was completed in 1642, at the peak of the Netherlands' golden age. It depicts the eponymous company moving out, led by Captain Frans Banning Cocq (dressed in black, with a red sash) and his lieutenant, Willem van Ruytenburch. With effective use of sunlight and shade, Rembrandt leads the eye to the three most important characters among the crowd, the two gentlemen in the centre (from whom the painting gets its original title), and the small girl in the centre left background. Behind them the company's colours are carried by the ensign, Jan Visscher Cornelissen.
The militiamen were also called Arquebusiers, after the arquebus, a sixteenth-century long-barrelled gun.
Rembrandt has displayed the traditional emblem of the Arquebusiers in the painting in a natural way: the girl in yellow dress in the foreground is carrying the main symbols. She is a kind of mascot herself: the claws of a dead chicken on her belt represent the clauweniers (arquebusiers); the pistol behind the chicken stands for 'clover'; and, she is holding the militia's goblet. The man in front of her is wearing a helmet with an oak leaf, a traditional motif of the Arquebusiers. The dead chicken is also meant to represent a defeated adversary. The colour yellow is often associated with victory.
http://en.wikipedia.org/wiki/Night_Watch_(painting)