The long battle between Louisville-based insurer Humana and Minnesota-based UnitedHealth over the awarding of the lucrative military Tricare contract is moving into a new venue. Humana lost the $23 billion contract to provide insurance to military families the South to UnitedHealth two years ago, but quickly challenged the ruling and won the appeal the next year.That victory was then challenged by UnitedHealth, but was upheld by the General Accounting Office.UnitedHealth is now suing the Defense Department in the U.S. Court of Federal Claims over its decision to give the contract back to Humana. The company has argued that Humana's cost savings were built on low reimbursements to doctors; Reimbursements that were so low, they could deter healthcare providers from seeing Tricare patients.