What was martin luther trying to accomplish when he nailed his 95 theses to the door of a church?

Luther's intention when posting the 95 Theses was to call the church back to doing what was right, rather than peddling indulgences as a way for people to make up for their sins.

Luther's 95 Theses are famous for starting the Reformation movement.  But it would be good for you to know that several weeks before the famous 95 Theses, Luther had writted "A Disputation against Scholastic Theology," a set of 97 theses aimed at the core teachings of the Roman Catholic church's main theological scholars.  This document didn't attract a lot of notice initially, because it was the sort of doctrinal debate university types would have with each other.  But after the controversy got started and Luther was called upon by his brothers in the Augustinian order of monks to defend his theology, the theology he defended was his attack on scholasticism.  At Heidelberg, in 1518, Luther spoke more fully about the central problem's of Rome's theological system.  Luther's emphasis in both 1517 documents (and in his career overall) was on salvation by grace alone, which contradicted Rome's system that portrayed God giving rewards to the acts we do by our own wills.