Contrary to popular belief, the Uniformed Services Former Spouse Protection Act (USFSPA) does not make division of retirement pay mandatory on divorce.
The act simply allows a state divorce court to treat military retirement pay as property of the military member, or joint property, depending on the laws of that particular state (in other words, if the state law allows division of civilian retirement pay for divorce, it will usually also allow division of military retired pay for divorce). The amount of division would be according to the laws of the state that the divorce was granted in.
The act also allows the military to pay the ex-spouse directly (if a court orders retirement pay division), if they were married for more than 10 years, with more than 10 years overlapping military service. If the marriage lasted for less than 10 years, or the couple's marriage did not overlap at least 10 years of service, the court can still order military retirement pay divided, but the military will not pay the ex-spouse directly. They would pay the member, and the member would be required to pay the court-ordered amount to the ex-spouse (or face possible contempt of court charges).
Complete details are available in the Article, Division of Retired Pay.