After more than four years into the war in Iraq, the public should note the congressional relief last week that comments offered by Gen. David Petraeus, the new commander of American forces there, were remarkable for their forthrightness. Certainly other military leaders have been candid and few shared former Defense Secretary Donald Rumsfeld’s myopic view of progress in Iraq, but Gen. Patraeus went further, forcing Congress into choices that not even the White House can control.

While acknowledging measurable progress in places such as Anbar province, where local leaders have cooperated with U.S. troops to reduce the violence there, Gen. Patraeus also said Iraq may get harder before it gets easier and that improvements will require “an enormous commitment” by the United States. He said, “there is vastly more work to be done across the board. … We are just getting started with the new effort.”

Gen. Petraeus has promised an assessment of the 28,000-troop surge by the end of August, at which time he is expected to describe where further progress has been made and what kind of challenges remain. But his comments last week should prepare the public for what to expect – the possibility of many more years, many more lives and hundreds of billions of dollars more. And that’s if things go well.

Sen. Susan Collins, who attended the general’s classified briefing and who opposed the surge, reflects the political middle’s view of conditions in Iraq. She said she was willing to wait until Gen. Petraeus’ next report, but “the surge really is the last option. The commitment can’t be open-ended. I want to see significant progress by then, not only improving security but also political reconciliation.” She would not have been cheered by the recent quarterly report by the Special Inspector General for Iraq Reconstruction Stuart Bowen, who urged Iraq to reduce corruption and increase the use of its own funds for reconstruction.

And if the progress isn’t apparent by fall, said Sen. Collins, “then we should redefine our mission and begin a gradual but significant withdrawal next year.”

The timelines in the supplemental spending bill, passed largely by Democrats and rejected by the president, are the first official turn toward what will arrive with Gen. Patraeus’ summer briefing. That’s when Congress will hear of more instances of progress but also of many more challenges ahead with years of fighting to shore up a shaky Iraqi government. Members of Congress will not have the reassuring words of previous military commanders to give them cover for their decisions, but only the hard-edged assessment of a general who sees hard choices over a long time.

Perhaps those hundreds of thousands of trained Iraqi troops that the administration has said were ready to go, really will be by then. Either way, look for withdrawal of U.S. troops in 2008.