It is often thought that Shakespeare wrote Macbeth specifically for King James VI of Scotland, who in 1603 became James I of England. There is a tradition that the play was first performed at court before the king, though there is very little evidence for this. What is clear is that the play was designed to appeal to the new King of England in a number of ways. It deals with two characters he believed to be his ancestors: Banquo and Fleance. Banquo is presented in a very positive light, as a noble foil to the villainy and treachery of Macbeth. James was also a learned authority on witchcraft, having published a book on the subject in 1597.

The appeal of a Scottish play, catering to the interests of the new king and featuring an account of how his ancestors came to power, seems clear enough for Shakespeare, who had made his reputation under Queen Elizabeth and was doubtless eager to secure the patronage of the current monarch, who was interested in literature and theater. However, it is important not to be too dogmatic in assigning to Shakespeare reasons for writing one of his greatest plays. He knew a good story when he saw it, and must have realized as he read the account of Macbeth's career in Holinshed's Chronicles that this could be adapted into a peerless psychological study of ambition, as well as a thrilling drama full of action and excitement. One of Shakespeare's most compelling reasons for writing Macbeth must have been that by this stage in his writing career, at the height of his powers, he was confident that he could create a masterpiece.

Shakespeare wrote Macbeth as a tribute to King James I, who had been crowned king of England three years before the play was probably first performed in 1606. The play is both laudatory towards James and a cautionary tale that can be described as an "advice to princes."

The Scottish setting is a tribute to James, who was king of Scotland before becoming England's king as well. James, who believed he could heal people of diseases such as scrofula with his royal touch, was flattered by being likened in act IV, scene 3 to King Edward the Confessor, another healer who was one of James's ancestors. James was also flattered in being a descendant of the "good" leaders like Malcolm, who defeated the tyrant Macbeth.

But the play also cautions the king not to become a tyrant. By 1606, it was clear that James I was not going to continue the policies of Elizabeth I which, while repressive by our standards, allowed people as much freedom as possible given the time period. As a woman and the daughter of a queen many thought was illegitimately placed on the throne, Elizabeth knew she had to tread very carefully to maintain public support. James had none of these compunctions and took a much more aggressive attitude towards his powers, leaning into the then-current idea of the divine rights of kings. This ideology offered him the maximum power to claim ownership of property and to rule without the advice of parliament. Shakespeare is warning James I through this play that tyranny breeds revolt and instability. Shakespeare was right: under James's son, the country would erupt into civil war over monarchial excesses.

The primary purpose of Shakespeare's writing of Macbeth was most likely to warn his fellow countrymen of the dangers of violent regime change.

Just a year before the play was written, a group of terrorists had come close to wiping out the entire political establishment, including the royal family, by blowing up the Houses of Parliament.

Had this audacious terrorist act succeeded, there's little doubt that England would've been plunged into chaos and bloodshed. Shakespeare didn't want that to happen, so he used his extraordinary skills as a playwright to drive home the message that changing the political system by force can come to no good.

That indeed is precisely what happens in the play. After Macbeth murders King Duncan and takes the throne, Scotland becomes a blood-soaked tyranny in which no one is safe from Macbeth's wrath and paranoia.

Had the natural order of things been allowed to take its course, with Duncan passing away and being succeeded by his son Malcolm, then none of this would've happened. A peaceful transition would've occurred between one reign and the next, ensuring the political stability that would've benefitted the people of Scotland as a whole.

It is precisely this kind of peaceful transition that Shakespeare himself endorsed for his native England, and whose importance he wished to convey in Macbeth.

Interestingly, Shakespeare wrote Macbeth as a tribute to King James, the new monarch of England at the time.  When Shakespeare wrote the play, he included several elements that would have appealed to the king: witchcraft and ancestry.  First, King James was previously interested in demonology, including witchcraft.  Several witches had been foiled in their attempt to place on a curse on James when he was king of Scotland.  As a result, James wrote a text entitled Demonology, which was offered to the public as his treatise on witchcraft among other things.  Clearly, Shakespeare uses this information as the basis for his 3 witches in Macbeth.  Next, Shakespeare wrote Macbeth to praise King James and his ancestry.  The character of Banquo was the ancestor of King James; you can observe this in Act IV when the witches show the apparitions of the 8 kings descending from Banquo.  The final king holds a glass in his hand.  In the staging of this scene, the final apparition would have held a glass (mirror) up towards James so that when James looked down at it, his reflection was seen in the mirror - thus insinuating that he was in the line of kings descending from Banquo and paying homage to James' lineage.

Shakespeare wrote "Macbeth" specifically for King James I. The king was a large supporter of the theater, and Shakespeare's company even became known as "The King's Men." King James I was king of Scotland and eventually became King of England; his ancestry could be traced back to Banquo, which was documented in the "Chronicles of England, Scotland, and Ireland" by Raphael Holinshed (1587). The "Chronicles" were a primary source for Shakespeare throughout the course of his career.

Why did Shakespeare write Macbeth for King James?

We don't know exactly why Shakespeare wrote Macbeth. While we have much documentary evidence that Shakespeare was Shakespeare, all of it is business related, such as contracts and wills: we have nary a shred of paper in which Shakespeare recorded a personal opinion or thought. We can only rely on his poetry and plays and larger historical currents to guide our thinking. Therefore, the best we can do is to make an educated guess.

Macbeth was written about 1606, shortly after James I took the throne in England and became patron of Shakespeare's theater company. We can surmise Shakespeare had two purposes in writing this play: to flatter James and to caution him.

The play flatters James, also king of Scotland, by being set in Scotland and showing his ancestor, Banquo, in a positive light. An allusion in the play to King Edward the Confessor curing scrofula was also a nod to James I, who revived the idea that the royal touch could cure illnesses.

Furthermore, Shakespeare showed he knew James's story well: James believed in witchcraft and thought that witches had raised a storm that threatened him and his wife as they set sail to Denmark. Shakespeare's acknowledgment of witches and their power would have played flattering tribute to James's worldview.

More importantly than these flattering little touches, however, is the overall theme of the play. English citizens, with good reason, feared James would veer into tyranny. He took an aggressive stance on the rights and power of the monarchy in a way that unnerved many. Shakespeare's play shows the ill effects of a tyrant on a country and on the tyrant himself, and thus Macbeth acts as cautionary tale or "advice to princes"—advising James to take it easy and steer a moderate course.

Why did Shakespeare write Macbeth for King James?

James I took Shakespeare's theater company under his patronage, and its name changed from "Lord Chamberlain's Men" to "The King's Men." Shakespeare played his political hand cleverly by writing a play that enhanced the moral virtues of Banquo, whom King James called his ancestor.

Shakespeare based his historical plays on Holinshed's Chronicles, in which Banquo is considered a historical figure. Later studies disputed such belief, but in the 17th century no one doubted that the House of Stuart descended from the first High Steward of Scotland who, in turn, was believed to have been Banquo's great-grandson. As you know, James was already king of Scotland when he ascended the English throne. 

In order to please his new benefactor -remember that Shakespeare had also found favor with Elizabeth I, James's predecessor- the Bard altered the information provided by Holinshed. While the Chronicles recorded that Banquo had been Macbeth's accomplice in the murder of Duncan and in the subsequent usurpation of the Scottish throne, Shakespeare portrayed him as an innocent spectator first and as a victim later. 

It stands to reason that James I would not have appreciated being associated to a murderer of kings. However, Shakespeare did include a hint that pointed to Banquo's devious behavior. After Duncan's death, Banquo is shown siding with Macbeth, when he should have supported Malcolm if he had been a loyal subject.

It is not clear why he did this. King James and his court did not notice the contradiction. If they had, Shakespeare's career would probably have ended then and there.   

Why did Shakespeare write Macbeth? What was the purpose behind it?

Macbeth wrote the play primarily because he was commanded to by King James I, thus the term "command performance."  Before reigning as King James I of England, he was known as James VI of Scotland.  Thus, a play set in Scotland and giving battle victory in Scotland would appeal to him.  In addition, the truly good character, Banquo, is modeled afer an actual relative of James, making his family look true and continually virtuous in the midst of all the betrayal around him.  He does not succumb to the witches prophecies as Macbeth does, thus preserving the family integrity.

More generally, Shakespeare wrote about the common man and his problems.  Ambition, greed and betrayal are unfortunately common to most readers, keeping the interest in this play alive for generation upon generation.