Body armor and helmets that were the wrong size. Bright orange life jackets that are of little use for tactical units that require camouflage. Vehicles that partner nations do not have the parts to maintain. These are just some of the issues that have plagued the Pentagon’s multibillion-dollar Global Train and Equip program, which bankrolls training, supplies and weapons to militaries of foreign nations, according to a new report from the Government Accountability Office. With $4.1 billion allocated to the program from 2009 to 2017, it is the United States’ third-largest security-assistance effort — behind those that fund the fight against ISIS in Iraq and Syria and the Taliban in Afghanistan. The Pentagon considers these partnerships essential to its global counterinsurgency efforts, but the G.A.O. found that only eight of 21 projects evaluated in 2016 and 2017 showed improved capabilities in the local military forces that the programs are meant to help.

The Global Train and Equip program was first authorized under the 2006 defense bill to build the capacity of partner nations to fight terrorist threats abroad. But poor project designs, procurement and equipment issues and work-force-management failures have limited its ability to help the militaries of partner nations to effectively fight terrorist groups on their own turf, according to the G.A.O.

Part of the problem has to do with the way the Defense Department decides what the money should accomplish and how. Colby Goodman, the director of the Security Assistance Monitor, a Washington think tank, noted that the G.A.O. report calls attention to the vague nature of the United States’ objectives in training and equipping each country. “What are the short-term and medium-term goals, and how do we think we can achieve that?” Goodman said. “We don’t have anything that says, ‘Here exactly is the strategy, and here are the indicators that they’re trying to achieve.’” He added that the report shows a Pentagon focus on terrorist groups, like Boko Haram in West Africa and the Shabab in East Africa, but for all the money being allocated, these militants have limited ability to harm the United States. “There’s not a lot of evidence that these groups are threatening the homeland, but they for sure can threaten U.S. Embassies and U.S. interests in these countries,” Goodman said. With more clarity about the true nature of the threats on the ground, aid programs could be subjected to a more stringent analysis of costs and benefits.