The composition of the painting was very different for the period. Instead of showing the figures in a neat orderly fashion, where everyone was given the same prominence and space on the canvas, Rembrandt has painted them as a busy group in action.
Around 1715 a shield was painted onto the Night Watch containing the names of 18 people, but only had ever been identified. (So remember if you paint a group portrait: draw a diagram on the back to go with the names of everyone so future generations will know!) In March 2009 Dutch historian Bas Dudok van Heel finally unraveled the mystery of who's who in the painting. His research even found items of clothing and accessories depicted in the Night Watch mentioned in inventories of family estates, which he then collated with the age of the various militiamen in 1642, the year the painting was completed.
Dudok van Heel also discovered that in the hall where Rembrandt's Night Watch was first hung, there were six group portraits of militia originally displayed in a continuous series, not six separate paintings as has long been thought. Rather the six group portraits by Rembrandt, Pickenoy, Bakker, Van der Helst, Van Sandrart, and Flinck formed an unbroken frieze each matching the other and fixed in the wooden paneling of the room. Or that was the intention... Rembrandt’s Night Watch doesn't fit with the other paintings in either composition or color. It seems Rembrandt did not adhere to the terms of his commission. But then, if he had, we'd never have had this strikingly different 17th century group portrait.
Find Out More:
Read up on the history and importance of the Night Watch on the Rijksmuseum website
Palettes of the Old Masters: Rembrandt
60-second Profile of Rembrandt from About.com's Guide to Art History