Almost all his works are portraits and even those that are not (some genre scenes, and an occasional religious picture) are portrait-like in character. He is said to have been taught in Haarlem by Karel van Mander, but there is no discernible influence from him in Hals's early works, which are not numerous or well documented. The earliest dated picture associated with him is Jacobus Zaffius (1611, Hals Mus., Haarlem; perhaps a copy), and on stylistic evidence a few other paintings can be dated around the same time. Nothing he did before 1616 anticipated the way he shattered well-established traditions that year with his life-size group portrait of the Banquet of the Officers of the St George Militia Company (Hals Mus.). There is no real precedent in either his own work or that of his predecessors for the vigorous composition and characterization of this picture, which has become a symbol of the strength and healthy optimism of the men who established the new Dutch Republic. It demonstrates to the full his remarkable ability—his greatest gift as a portraitist—to capture a sense of fleeting movement and expression and thereby convey a compelling feeling of life.From 1616 onwards there are numerous dated or documented works by Hals and his artistic development is clear. He was at the height of his popularity in the 1620s and 1630s. During these decades he made five large group portraits of civic guards: one (finished by Pieter Codde) is in the Rijksmuseum and the others are in the museum named after Hals in Haarlem, the only place where one can get a comprehensive view of his range and power. In the 1630s his compositions became simpler and monochromatic effects took the place of the bright colours of the earlier paintings (Lucas de Clercq and Feyntje van Steenkiste, 1635, Rijksmuseum, Amsterdam). The group portrait of the Regents of the St Elizabeth Hospital (1641, Hals Mus.) sets the key for the sober restraint of the late period, when his pictures became darker and his brushstrokes more economical. His career culminated in his group portraits of the Regents and the Regentesses of the Old Men's Alms House (c.1664, Hals Mus.), which rank among the most moving portraits ever painted. By this time Hals was using in his commissioned portraits the bold brushwork and the alla prima technique that early in his career he reserved for genre pictures. No drawings by him are known and he presumably worked straight on to the canvas.Hals had two painter brothers and five painter sons, but the only artist of substance among them was his brother Dirk (1591–1656), who painted charming small interior scenes. Apart from his sons, Hals taught numerous pupils, including (with varying degrees of certainty) Judith Leyster, Jan Miense Molenaer, Adriaen van Ostade, Adriaen Brouwer, and Philips Wouwerman. His reputation did not long outlive him, however, and it was only in the second half of the 19th century that there was a renewed appreciation of his genius. The spontaneity of his work appealed to the generation of the Impressionists, and from about 1870 to about 1920 he was one of the most popular of the Old Masters, becoming a model for society portraitists. Lord Hertford's purchase of his most famous work, The Laughing Cavalier (1624, Wallace Coll., London), in 1865 for the then enormous sum of 51,000 francs (more than six times the auction estimate) was a milestone in the revival of his fortunes, and the buoyant confidence of his paintings later made him a particular favourite with the new generation of fabulously rich American collectors—self-made men—who were beginning to dominate the picture market. This explains why so many works by him are in American collections.