W.D. Gann, also known as William Delbert Gann, was a financial trader, analyst and author who lived in the early 20th century. He is widely considered to be one of the most successful traders of his time, and his methods and theories are still studied and used by traders today.

Gann's primary focus was on market forecasting using geometric angles and time cycles. He believed that the movements of financial markets could be predicted using mathematical and geometric principles. He developed a number of techniques for analyzing charts, including the use of angles, which he believed revealed the underlying trend of the market. He also used time cycles to predict market turning points, and believed that certain dates were more significant than others in the market's movements.

Gann also placed a strong emphasis on the importance of understanding the fundamentals of the markets, and believed that a trader should have a deep understanding of the underlying economic and political factors that drive market movements. He believed that the most important factors in determining market movements were supply and demand, interest rates, and the overall state of the economy.

One of Gann's most famous contributions to trading analysis is the "Square of Nine," also known as the "Square of 144." This is a geometric chart that Gann developed, which he believed could be used to predict market movements. The chart is based on the number 9, which Gann believed had special significance in the markets. He believed that the Square of Nine could be used to identify key levels of support and resistance in the markets, and that it could be used to predict market turning points.

Gann's methods and theories were not without controversy, and some traders and analysts have criticized them for being overly complex and difficult to apply in practice. However, many traders still find value in his work, and Gann's methods continue to be studied and used by traders and analysts today.

Gann's work has also influenced many other traders and analysts in the field, including Ralph Elliott, who developed the Elliott wave theory, which is based on the idea that market movements are fractal and repetitive in nature. Gann's work also influenced other trading gurus like R.N. Elliott, and W.D Gann's work is considered as a foundation of the technical analysis.

In conclusion, W.D. Gann was a pioneering trader, analyst, and author of the 20th century whose methods and theories are still studied and used by traders today. His focus on market forecasting using geometric angles, time cycles and understanding the fundamentals of the markets, has been a great contribution to the field of trading analysis. Despite some criticism, Gann's work continues to be studied and used by traders and analysts today and his work has also influenced many other traders and analysts in the field.