It seems that people don't learn from history very often. But perhaps when it really counts, as in when we wage war, people are better at learning from history. Is there any historical studies that prove we have progressively gotten better at waging war and learn from our mistakes or do we continue to screw up like we do in all other non-war efforts?
This is a tough question to answer for a few reasons. The first is that war is by nature adversarial; when "we" get better at waging war, and other people get better at waging war, the likelihood of victory is the same. In other words, even if we are learning, as long as the people we fight against are also learning, there are no clear gains made.
The idea of "we" is problematic as well. Does it mean military strategists? Politicians? The people? Also, what lessons would we learn? To avoid war? To win wars? But all of these points are really avoiding the question so I will leave you with two answers.
We cannot say we have gotten better or worse at waging war because "success" is a largely subjective measure. Dominic Johnson and Dominic Tierney explore this idea in Failing to Win. From the "About this book": "Why, for instance, was the Mayaguez Incident in May 1975—where 41 U.S. soldiers were killed and dozens more wounded in a botched hostage rescue mission—perceived as a triumph and the 1992–94 U.S. humanitarian intervention in Somalia, which saved thousands of lives, viewed as a disaster?" Essentially, some wars or military operations are deemed failures despite objective successes whereas others are deemed successes despite objective failures. The idea of success or failure is heavily influenced by media and political considerations. Furthermore, these ideas of success/failure influence policy decisions in the future. Because of perceived failures in Somalia, leaders were hesitant to get involved in another mass atrocity in Rwanda. Because of inaction in Rwanda, leaders were more anxious to get involved in Kosovo. Which brings us to a second answer.
Perhaps we have learned, but we often learn the wrong lessons from history. Or rather, we learn "lessons" when there may be no "lessons" to learn at all. Eliot Cohen offers several warnings to military strategists and historians in "The Historical Mind and Military Strategy" Less trained minds are apt to make poor analogies or believe that just because something has happened in the past it is bound to reoccur in the future. However, well trained minds learn to look more closely at the nuances underlying past events. Cohen actually explicitly discusses the idea of "lessons learned" as reductionist and removed from context. In short, we do not seek to uncover concrete policy decisions by studying history, but rather to develop a mind that can examine and critique a given situation.