The private equity firm Ares Management LLC last Thursday said it has agreed to acquire Global Defense Technology & Systems, Inc. [GTEC] in a deal valued at $315 million, adding to its portfolio a provider of software and information technology services and solutions to the federal government.

The deal includes a $24.25 cash tender offer for GTEC’s shares, which represents a 51 percent premium over GTEC’s closing stock price last Wednesday, and the assumption of debt prior to expenses. The transaction has been approved by GTEC’s board of directors and is expected to close in the second quarter of 2011. The deal must also go through federal regulatory review.

“Ares Management will partner with GTEC’s management team to help support our growth as the leading mid-sized national security company,” John Hillen, president and CEO of GTEC, said in a statement.

GTEC’s customers include the Defense and Homeland Security Departments, the intelligence community, federal law enforcement agencies and other federal government customers involved in national security.

Terms of the deal allow GTEC to continue to solicit alternative acquisition proposals through April 1. GTEC’s financial adviser on the deal is Cowen and Co. and Ares’ is Wells Fargo Securities.