In an argument with his oldest son in 1581, the murderous, paranoid Ivan became enraged and struck him on the head with his staff. The wound was fatal and the son died four days later. The heir to the throne was now Fyodor, who was unfit to rule the country.
While most people reviled Ivan, some admired him. Almost four centuries later, Stalin, the murderous, paranoid dictator of the USSR, praised Ivan and the Oprichniki as "progressive" forces in building the Russian state and suppressing rebellious subjects. Stalin's secret police would do similar for the USSR, on a massive scale involving the torture, imprisonment, and deaths of millions.
Ivan IV, became a monster, to his enemies, to his people, to his court, to his family, and even to himself, well earning his nickame, "Ivan the Terrifying". This side of him developed over the course of his reign, and his early years as Tsar saw him enact useful reforms for Russia.
Some of his later behavior was influenced by his childhood experience. His father, Vasiliy III, Grand Prince of Moskva, died of natural causes when Ivan was three years old. Ivan was proclaimed Grand Prince of Moskva, with his mother, Elena Glinskaya, governing as regent for Ivan. Her reign faced problems, including that both of Vasiliy's younger brothers became suspected of wishing to become the grand prince at Elena's and Ivan's expense. Both were eventually imprisoned and soon died in prison. Elena herself died only five years after becoming regent, and many believe she was poisoned. After her death, powerful clans of Russian nobles violently competed for control of Ivan and through him the state. All this affected Ivan, who would increasingly mistrust his nobles throughout his life.
When Ivan turned 16, he assumed power in his own right and had himself crowned as Tsar and Grand Prince of All Rus. Ivan's grandfather, Ivan III ("Ivan the Great") had been crowned Grand Prince of Moskva and later assumed the title Grand Prince of All Rus. He came to call himself tsar (emperor) during his reign but did not make this an official title. Ivan IV made it official.
Ivan embarked on a series of reforms for Russia, improving government administration, the military, Russian law, and the Orthodox Church in Russia. He introduced a partially-elected advisory "assembly of the land" of nobles, churchmen, landowners, and city dwellers. He brought the first printing press to Russia. He sought foreign assistance by recruiting German craftsmen to come to Russia, but this was blocked by Poland-Lithuania (still separate countries but with a common monarch). He also sought trade and greater contact with western Europe, but his attempts to expand into Livonia (what is now Estonia and Latvia) and open a direct sea route to the west caused a long war with not only the Livonian Order but also a shifting alliance of Poland-Lithuania, Sweden, and Denmark, all who opposed Russian westward expansion. As the war dragged on, Russian troops became infamous for cruelty to their opponents and civilians. After 25 years of on-and-off conflict, the war ended in Russian defeat and some territorial losses in the Baltic area.
In the south and east, however, Ivan succeeding in conquering several Muslim khanates that had formed out of the Golden Horde. Again, his conquests were cruel, and the city of Kazan was devastated after it fell to him.
Ivan, however, was mental instable. He was increasingly suspicious of others, which grew to outright paranoia, and was more-and-more prone to violent rages. He could be very cruel and used torture not only for state purposes but for his personal enjoyment. He became worse after a serious illness and when his first wife died. He suspected, perhaps correctly, that she had been poisoned. Russian nobles were eager to gain favor and privileges by marrying one of their daughters to the Tsar, and it is possible that one had the tsar's wife poisoned. In response to the death, Ivan had several nobles tortured and executed.
Ivan's paranoia against nobles increased when some nobles turned traitor. One powerful noble in particular defected to Lithuania and led Lithuanian troops to devastate part of Russia. Ivan used this and other incidents to demand absolute power. Although the earlier rulers of Russia had great power, there were political and religious traditions that imposed some limits on them. Ivan overcame this, making the tsar absolute ruler or "autocrat" (eventually this became one of the official titles of the monarchy), which would last until the early 20th Century. Ivan now had the unrestricted power to execute traitors and confiscate their estates. He soon raised the Oprichniki as his own paramilitary force to enforce his will and rewarded them well. When Ivan became suspicious that the nobles of the city of Novgorod were plotting treason, intending to make the city part of Lithuania, he ordered the Oprichniki to raid the city. Over perhaps five weeks, thousands were tortured and killed, while the city itself was pillaged and burned. Novgorod has been a major Russian city but never recovered from this calamity.
The Oprichniki became feared everywhere in Russia and succeeded in Ivan's goal of terrorizing his subjects. They wore black, suggestive of Russian monks but devoted to Ivan rather than God. They rode with severed dogs' (sometimes wolves') heads and brooms as symbols that they would sniff out the tsar's enemies and sweep them away. As almost every knew well, "sweeping" often meant torture and sometimes execution, with the victims having no legal rights. Ivan himself rode with a mechanical iron dog's head, and he would watch or participate in the torture and killings. With their cruelty and their relentless pursuit of real and imagined traitors, the Oprichniki foreshadowed Stalin's NKVD secret police, who would terrorize the USSR on a much greater scale. The success of the Oprichniki, however, led to their downfall, as Ivan overestimated their abilities and loyalty. When a huge Crimean Tatar army raided Russia, Ivan ordered the Oprichniki to fight them, but many refused to take the field and the ones that did (along with the regular Russian army) failed to stop the raid. Moskva was burned and looted, with great loss of life. Ivan disbanded the Oprichniki and forbade anyone to mention their name again.
Ivan ruled for just over 50 years, growing worse in behavior. He developed a bone disease that made it very painful to move, and he used medicines containing mercury that perhaps caused mercury poisoning, likely worsening his mental condition. He increasingly argued with his son and heir, also named Ivan. One day, Ivan the Terrifying took offense at the clothing the younger Ivan's pregnant wife was wearing and beat her (she later had a miscarriage). The beating led to the son and Tsar arguing so forcefully that Ivan the Terrifying became enraged and struck his son with his staff. The young Ivan soon died from his wounds, leaving the Tsar with only an incompetent son, Fyodor, for heir. Ivan the Terrifying died a few years later, and Fyodor would be the last of Russia's Rurik dynasty that had began with Rurik the Varangian centuries earlier.