The first translations of Sun Tzu into Englis can in the early 20th century. The "public domain" versions of Sun Tzu's The Art of War that are available today are all based on these early translations. These versions were in turn based on various fragmentary Chinese sources. These versions included a number of rather flagrant mistakes in translation.
The first English translation of The Art of War is less than a hundred years old. Captain E. F. Calthrop published the first English translation in 1905. Lionel Giles, an assistant curator at the British Museum and a well-known sinologist and translator, attacked this early translation, and he published his own version in 1910. This Giles version, though itself from a fragmentary manuscript, is still used broadly today as the basis for the popular "Clavell" Art of War version.
Both of these versions were greatly improved by the work of Samuel Griffith on The Art of War, who published his Art of War in 1963, including a number of historical Chinese commentaries on the text. Not the least of Griffith’s strengths was his experience in the military and knowledge of military history as a brigadier general in the U.S. Marine Corps. However, this was also his version's greatest flaw. Griffith did not really believe or understand all of Sun Tzu and would often explain away Sun Tzu's direct statements without making it clear that this was his commentary and not what Sun Tzu wrote. Griffith was also not much of a writer. By our standards today, much of Griffith’s language is awkward and dated. To read more about the Griffith Art of War translation, click here.