The "history plays" written by Shakespeare are generally thought of as a distinct genre: they differ somewhat in tone, form and focus from his other plays (the "comedies," the "tragedies" and the "romances"). While many of Shakespeare's other plays are set in the historical past, and even treat similar themes such as kingship and revolution (for example, Julius Caesar,Antony and Cleopatra,Hamlet, or Cymbeline), the eight history plays have several things in common: they form a linked series, they are set in late medieval England, and they deal with the rise and fall of the House of Lancaster--what later historians often referred to as the "War of the Roses."
Shakespeare's most important history plays were written in two "series" of four plays. The first series, written near the start of his career (around 1589-1593), consists of Henry VI, Parts 1, 2 & 3, and Richard III, and covers the fall of the Lancaster dynasty--that is, events in English history between about 1422 and 1485. The second series, written at the height of Shakespeare's powers (around 1595-1599), moves back in time to examine the rise of the Lancastrians, covering English history from about 1398 to 1420. This series consists of Richard II,Henry IV, Parts 1 & 2, and Henry V.
Although the events he writes about occurred some two centuries before his own time, Shakespeare expected his audience to be familiar with the characters and events he was describing. The battles among houses and the rise and fall of kings were woven closely into the fabric of English culture and formed an integral part of the country's patriotic legends and national mythology. This might be compared to the way in which citizens of the United States are still aware of the events and figures surrounding the American Revolution, which occurred more than two centuries ago--although, like the English commoners of Shakespeare's time, most American do not know this history in great detail. Shakespearean history is thus often inaccurate in its details, but it reflects popular conceptions of history.
Shakespeare drew on a number of different sources in writing his history plays. His primary source for historical material, however, is generally agreed to be Raphael Holinshed's massive work, The Chronicles of England, Scotland and Ireland, published in 1586-7. Holinshed's account provides the chronology of events that Shakespeare reproduces, alters, compresses, or conveniently avoids--whichever serves his dramatic purposes best. However, Holinshed's work was only one of an entire genre of historical chronicles that were popular during Shakespeare's time. He may well have used many other sources as well; for Richard II, for example, more than seven primary sources have been suggested as having contributed to the work.
It is important to remember, when reading the history plays, the significance to this genre of what we might call the "shadows of history." One of the questions which preoccupies the characters in the history plays is whether or not the King of England is divinely appointed by the Lord. If so, then the overthrow or murder of a king is tantamount to blasphemy, and may cast a long shadow over the reign of the king who gains the throne through such nefarious means. This shadow, which manifests in the form of literal ghosts in plays like Hamlet,Macbeth,Julius Caesar, and Richard III, also looms over Richard II and its sequels. The murder of the former King Richard II at the end of Richard II will haunt King Henry IV for the rest of his life, and the curse can only be redeemed by his son, Henry V. Similarly, Richard II himself, in the play which bears his name, is haunted by a politically motivated murder: not of a king, but of his uncle, Thomas of Woodstock, Duke of Gloucester. This death occurs long before the beginning of the play, but, as we will see, it haunts Richard, just as his own death will haunt the usurper who is responsible for it.