(Reuters) - Activist investor Carl Icahn on Tuesday abandoned his effort to acquire control of U.S. truck and military vehicle maker Oshkosh Corp <OSK.N> after shareholders tendered fewer shares than he had hoped for.

Only 22 percent of shares were tendered in his $32.50 per share offer, less than the 25 percent threshold Icahn had sought. Icahn, who remains Oshkosh's largest shareholder with a 9.5 percent stake, had said that many shares would have improved his chances of overhauling the board of the Oshkosh, Wisconsin-based company.

"We are returning all tendered shares and we will not extend the offer," said Icahn, whose offer valued Oshkosh at $2.98 billion and represented a 21 percent premium on the share price prior to his October bid.

This was Icahn's second run at Oshkosh; a year earlier he waged an unsuccessful proxy battle, with shareholders rejecting his slate of directors.

(Reporting By Scott Malone; Editing by Gerald E. McCormick)