This is a tough topic. I've struggled a lot with the problems of history, ideas such as "history is written by the winners" and so forth. However, like so many other cliches, it both has much truth and is misleading at the same time. I didn't start to write down my thoughts but once I got started a little, I got caught up in the challenge.
I once had to write an article about the attack on Pearl Harbor. I turned to contemporary newspapers and magazines of the United States and of Japan in order to see what the people thought of each other as the war approached. It was clear that many Japanese saw their island being cut off from the raw materials needed for a healthy economy. Perhaps if the US had understood that position better, the warlords of Japanwould not have ascended to the kind of control of the society they did and at least a part of the war in Asia could have been avoided. Writing history from the point of view of the victor may be initially satisfying but it leaves out information that may help provided guidance to action in the future.
Much of the criticism of American history that comes from ordinary Americans today is based on work by historians who continually re-examine the source materials of other times through the prism of today's values.
To look at it a different way: If you read two sportswriters description of a two hour contest, if the reporters are good, you will see two very different versions of why that particular game turned out the way it did. Of course, the central action will be more or less identical but the reasons, the value judgments, attributions of motive, emphases - these will all be different.
Now, add to that the stories of each of the athletes, the contest from their standpoints. One might be aging and would describe the two hours in a way that emphasized that. Another might tell the day's events from a point of view of how he played with pain, another how a self-help program was working, etc. The coaches, the owners, the manufacturer of the uniforms and of the equipment, the groundskeeper, the scorekeepers, the band, each would see the event in a different light, give different weights to the outcome's impact on the future and each would have something valid to add to the history of the game that day as would a sports historian who might put the present rules of the game in historical perspective and how the changes over the year effected that particular outcome.
What was involved? Perhaps one and a half dozen athletes and two hours of action - a pretty circumscribed activity.
So when a historian looks at "The Fifties" or World War II, or the reasons leading up to the Civil War when people changed the public and private motives over the course of the war, even a major work from an unusually informed source such as Churchill's World War II epic can only tell part of the story.
For those who want to approach the truth, it takes more than reading one historian. A good historian uses facts to open the reader's mind to currents that flow through history - he tries to answer the impossible question, "Why?"
It takes the reading of a wide variety of books written from differing points of view as well as source materials (newspapers, diaries, eyewitnesses). Then, filtered through your own interests, prejudices, etc. an depending on how well you have trained your mind to be open and critical, you will have earned your view of "history".
However, you always will have to condense and you will always have to organize and there will always be more to learn. Some of what you learn confirms what you already believed, some contradicts or modifies it.
I approached my first meeting with an established historian in my own field with some trepidation. He had studied "my" period for twenty years more than I had. I had read his work as a part of my education. However, he had not stopped learning. What I discovered was that he found my viewpoints based on my own original research, to be of some value. He was able to take parts of my work and incorporate the new information into his views. He had an open mind and his view therefore was broadened a small bit by my little contribution.
To expect "truth" is unreasonable. To keep an open mind, to train yourself to evaluate new information, to test it, and you stand a good chance of truly learning something valuable from the experience of others.
The problem is that it is soooo comforting to have an opinion and an opinion that fits into preconceptions is especially comfortable.