IRS publication 525 advised e a military disability rating of 20% or higher is eligible to recoup money deducted from their retirement pay for previous years. How?

IRS publication 525 updated in 2016 to advise a military disability rating of 20% or higher is eligible to recoup money deducted from their retirement pay for previous years.  How would I go about doing tha?  Which forms need to be filed to recover monies due for previous years.