King Richard II is today considered one of Shakespeare’s most important history plays and one with many unique qualities. In writing King Richard II in 1595, Shakespeare was returning to the subject of English history which had led to four plays a few years earlier in his career-- 1, 2, and 3 Henry VI and Richard III (the so-called first historical tetralogy), probably written and performed between 1591 and 1593. King Richard II in turn was the first of four additional connected history plays (the “second tetralogy”) depicting events in the era preceding the earlier ones. The first tetralogy had depicted the bloody Wars of the Roses, an aristocratic civil war between the houses of York …
Grady, Hugh. "Richard II". The Literary Encyclopedia. First published 15 September 2004; last revised 30 November -1.
[http://www.litencyc.com/php/sworks.php?rec=true&UID=2372, accessed 28 April 2015.]