Great powers rise and fall.

And a powerful member of the House of Representatives, mindful of this, fears the United States could be swamping itself in Afghanistan’s rugged terrain, a graveyard of foreign forces. USA/

“What I’m worried about is the cost of the war,” said Rep. John Murtha, who controls the Pentagon’s purse strings as chairman of the House Appropriations Defense subcommittee.

President Barack Obama, a fellow Democrat, was “real good” in presenting his new war strategy Tuesday night, “but he didn’t convince me,” Murtha told a briefing on Wednesday. He spoke after a two-day visit to Afghanistan last week.

The blunt, 77-year-old retired Marine said he had sent the president a copy of “The Rise and Fall of the Great Powers,” a 1987 study by Paul Kennedy, a Yale University professor of history.

The book, subtitled “Economic Change and Military Conflict from 1500 to 2000,” surveyed shifting balances of power that brought all empires to dust as they overextended their reach.