Anna (often referred to as "Anna Ivanovna" to avoid confusion with her cousin Anna {Petrovna}) was the daughter of
Tsar Ivan V of
Russia. When
Peter II died without naming an
heir in
1730, there were no remaining
male-line descendants of
Romanov tsars; however, there were several possible members of the
royal family in the female line. The only male was three-year-old
Peter, son of the late Anna Petrovna (daughter of
Peter the Great and
Catherine I); there were also
Elizabeth Petrovna, the late Anna's sister, and the two daughters of Ivan V, Catherine and Anna Ivanovna. Catherine was thought to be too much under the influence of her husband, the Duke of Mecklenburg; Elizabeth was considered too frivolous, and Peter too young. The daughters of
Catherine I were also excluded because of their mother's low birth. This left Anna Ivanovna,
widow of the
Duke of
Courland, as the choice of the Supreme Privy Council in Russia.
Anna had been living in Courland for ten years, a Russian woman among foreigners who did not want more Russian influence, and never had enough money to live as a duchess was expected to. It was a surprise to her to be offered the Russian throne, although it was with some conditions attached. She was not to be allowed to name her own heir, and her power was generally limited by the Privy Council. Anna accepted the limits and came to Moscow, but on finding that the majority of the nobles thought the Privy Council was just keeping itself in power, she led the Palace Guards in a limited revolution in which she tore up the conditions and declared herself absolute ruler in the traditional Russian way.
Many historians say that during this period the real power was Anna's German lover Ernst-Johann Biron. However, some things had to get done without either of them, as Anna generally insisted Biron spend as much time as possible with her (though he was married to someone else). Biron and some of Anna's other favorites were unpopular because they were foreigners; some historians characterize Anna's reign as the rule of the "German party." There is no real evidence that foreigners had any special position; in fact, during Anna's reign was the first time Russian army officers were paid as much as foreigners of the same rank in the Russian army. The position of the Orthodox Church did not change during her reign, but the Old Believers who would not accept the reforms from the time of Tsar Alexei were persecuted much more than they had been since then.
From 1735 to 1739 Russia again fought the Ottoman Empire to try and gain access to the Black Sea. The war was inconclusive, but is definitely evidence that Russia was interested in the same goals as it had been for the past century, and not those of the Germans.
Anna was an unsophisticated woman, who enjoyed such pastimes as shooting and watching dwarfs, monkeys and jesters. She was tall, heavy, and physically strong, and was generally not considered all that attractive by people who wrote down descriptions of her. When a matter interested her, she was very detail-oriented; it's just that she wasn't usually interested in politics and was happy to leave ruling to Biron and other ministers, with the power to override them if necessary. She died after a brief illness on 17 October 1740, having named her sister Catherine's just-born grandson Ivan VI as her heir.
Sources: Robert K. Massie's Peter the Great: His Life and World, Donald Raleigh and A.A. Ishkanderov's The Emperors and Empresses of Russia: Rediscovering the Romanovs, as well as those listed under Monarchs of Russia.