What I am about to quote is just from Wikipedia and I realize it has been flagged as biased, but the studies it quotes are studies. The drug war is surely an excuse to fund the defense industry and justify militarization, and I am convinced that in practice it is also a war over the drug trade, not against it.
In 1986, the US Defense Department funded a two-year study by the RAND Corporation, a private organization with a long and close relationship with the U.S. government , which found that the use of the armed forces to interdict drugs coming into the United States would have little or no effect on cocaine traffic and might, in fact, raise the profits of cocaine cartels and manufacturers. The 175-page study, “Sealing the Borders: The Effects of Increased Military Participation in Drug Interdiction,” was prepared by seven researchers, mathematicians and economists at the National Defense Research Institute, a branch of the RAND, and was released in 1988. The study noted that seven prior studies in the past nine years, including one by the Center for Naval Research and the Office of Technology Assessment, had come to similar conclusions. Interdiction efforts, using current armed forces resources, would have almost no effect on cocaine importation into the United States, the report concluded. 
President George Bush Sr. disagreed, arguing that “the logic is simple. The cheapest way to eradicate narcotics is to destroy them at their source….We need to wipe out crops wherever they are grown and take out labs wherever they exist.” 
During the early to mid-1990s, the Clinton administration ordered and funded a major cocaine policy study, again by RAND. The Rand Drug Policy Research Center study concluded that $ 3 billion should be switched from federal and local law enforcement to treatment. The report said that treatment is the cheapest way to cut drug use, stating that drug treatment is twenty-three more times effective than the supply-side “war on drugs”.  President Clinton’s drug czar’s office disagreed with slashing law enforcement spending.