After the terrorist attacks in the United States on September 11, 2001, and the war in Iraq and Afghanistan that followed, the debate about counterinsurgency (COIN) has once again been stirred up. Some researchers claim that the old proven theories and methods of successful COIN are still relevant. Other researchers, however, consider that today's opponents have developed and differ compared to the earlier, claiming that yesterday's theories are out dated and inadequate in a modern context. Today's view of successful counterinsurgency is heavily influenced by David Galula, whose theories were developed in the 1950s and 1960s. The purpose of this study is to investigate whether past theories are useful in contemporary insurgency. To investigate the question, the study examines whether the United States followed Galula's strategies in practice during the counterinsurgency in the Al-Anbar province (2003–2008). The study's findings indicate that there are similarities between U.S. action in Al-Anbar and Galula's models for successful COIN. Galula implies that the local population's support needs to be gained in order to achieve success in counterinsurgency. The focus on the population is clearly reflected in the U.S. approach and can be interpreted as the cause of success. In addition to similarities regarding the central parts of the theory, differences can also be found. In the two cases studied, the importance of cooperation with local armed forces and the media's role in the conflict is clearly highlighted, which is not mentioned in Galula's theory. Therefore, it cannot be excluded that other aspects not declared in Galula's theory might have influenced the outcome of the conflict as well. To be able to determine the usefulness of Galula's theory in modern time with greater certainty, further research is proposed to investigate more recent cases, using the results of this study as a starting point.