The Pentagon paid $458 million to train Afghan intelligence officers since 2010, but a lack of oversight made it difficult to measure whether the effort led to any improvements in the country's operations, according to an inspector general report released Monday.

Many of the Afghans trained specifically to be government ministry trainers and instructors never completed all their course work, and more than half of the sites created for intelligence training and mentoring were not fully transferred to the Afghanistan government as planned, the special inspector general for Afghanistan reconstruction found in its investigation.

"Although the … programs provided some assistance to the [Afghan National Defense and Security Forces], it is almost impossible to assess whether this assistance was worth the $457.7 million spent on these programs," SIGAR reported.

U.S. work on improving Afghan intelligence operations began in earnest in 2007 as Marines were facing roadside bombs. The Army began issuing contracts in 2010 for the training and mentoring program aimed at getting better intelligence about the country's insurgency.

Army Contracting Command issued contracts from 2010 and 2015 to provide the training courses and facilities to the Afghan forces. The prime contractor was Imperatis Corporation, New Century Consulting Limited was a subcontractor.

The program fully trained 70 out of 71 student officers in the Afghan National Army, but others did not complete the course work, according to SIGAR.

The office found that only 10 of the 24 police intelligence students completed all the courses need to be Ministry of Interior trainers. In addition, only one out of six Afghan National Army students completed any course work to be Ministry of Defense instructors.

Meanwhile, only 59 out of 125 U.S.-funded training and mentoring sites were fully ready to be transferred to the Afghan government, SIGAR found. The remaining sites were partially transferred or not transferred at all.