Beginning almost simultaneously with the surrender, the Investiture Controversy took Henry's full attention in the years that followed. Unrest in Saxony also flared up during this period again and again, but did not reach the same level of political and military as in the time from 1073 to 1075. At the diet of princes in Trebur in October 1076, Otto of Northeim again aligned himself with the opposition. Although he was always a potential candidate, the princes did not choose him; instead, in 1077 in Forchheim, they selected Rudolf of Rheinfelden and, later, Hermann of Salm as antikings. Nevertheless, Otto's had a significant influence on the opposition's politics. Militarily, he distinguished himself again in the battles of Mellrichstadt, Flarchheim and the Elster, leading from the front. Even Henry's son, King Henry V of Germany, still had to fight the Saxons. He lost, for example, the 1115 Battle of Welfesholz to the Saxons led by his later successor, King Lothair III.
Question: How many years did the political and military reach it same level?
Answer: 2