Whilst I was not consciously aware of it as I was working on his character, I realise a posteriori that my version of Heinrich IV owes something to Shakespeare - or perhaps to Saxo Grammaticus, the source of Shakespeare's Hamlet.
Although King Hamlet and King Heinrich share the same initial, I am by no means suggesting that Saxo, born about 50 years after Heinrich's death, took inspiration from the German king. Sure, there was a solid relationship between the German and Danish royal houses, cemented before Heinrich's birth by his father's first marriage to one of Knut the Great's daughters. Besides, a Danish (Saxon?) historian was bound to be familiar with the plight of the German child king, given the impact that his kidnapping, the regency, and his later struggles with the Saxons and Rome, would have on the neighbouring kingdom. The elements of Hamlet that seeped into my re-writing of Heinrich have got to with his personality, his relationship with his mother, and his political and personal relationship with key members of his court.
Like Hamlet, Heinrich lost his father, and that left his mother, Dowager Empress Agnes, as de facto ruler of the German kingdom and the Holy Roman Empire. Unlike Hamlet's Gertrud, she did not re-marry, yet the young widow attracted gossip and slander, including that she had an affair with her chaplain Siegfried, whom she raised to a bishopric. Her relationship with the nobleman Rudolph of Rheinfelden, whom she raised to the prestigious Duchy of Swabia, has also been the subject of scrutiny. Rudolph was a shady character - an excellent blueprint for both Polonius and Claudius. Yet every time her son and Rudolph clashed the Empress would do out of her way to pacify them. Eventually, as Lotharingia's sequel will show, Polonius morphed fully into Claudius: Rudolph exploited the Empress's favour to spin a treasonous network of alliances, attempting to snatch Heinrich's crown.
Like Hamlet, Heinrich grew up in a court rife with intrigue, where he would have repeatedly feared for his life. Kidnapped from his mother at eleven by Otto, Duke of Bavaria and Anno, Archbishop of Cologne, he will grow to distrust both the Empress and her enemies. As he came of age, he despatched his regents and later a few of his advisors, including his mother, in dramatic and sudden fashion, His demise of the almighty Archbishop Anno, and his attempt to frame his other kidnapper Duke Otto for treason - a move he will later repeat with Duke Rudolph, feels like Hamletic revenge. His later challenge to Rome, the excommunication, and the volteface with Pope Gregorius, could also be framed by the psychological traumas of his childhood.
Did the treacherous and at times treasonous environment of his upbringing turn him into a monster? Like for Hamlet, it is impossible to tell. His refusal to stay married to a woman he did not love, against all conventions of royal marriage, shocked his contemporaries yet also reveals an idealistic streak. His frontal attack on the Roman Church known as the Investiture Controversy makes it impossible to recover his true motives and thoughts. We know that this man who was excommunicated twice saw himself as the true head of the German Church, and was a passionate cathedral as well as castle builder. We know that his sons rebelled against him, accusing him of all sorts of sins. We know that despite his flaws he was loved by at least some of his people. We also know that Hugh of Cluny, his godfather who outlived him, never completely gave up on him. We also know that despite waging war against him, in later life Matilde fought to secure him a dignified burial. Would she have done so for a monster?
Perhaps, like Hamlet's, Heinrich's true problem was not metaphysical, but political. The dilemma was not 'to be or not to be,' but rather 'to be or not to be king,' when you have been exposed since your early years to the human and moral price.