Fort Riley ? With the Afghanistan war’s endgame approaching, the Army’s storied 1st Infantry Division is preparing to take command in the eastern provinces, where the strategy calls for a renewed push this year even as U.S. and allied forces draw down in less violent parts of the country.

After months of carefully sequenced training at Fort Riley for what will be its first Afghanistan command tour, the 1st Infantry will take over in April for the 1st Cavalry Division in a mostly mountainous sector that spans 14 provinces and includes 450 miles of the Afghanistan-Pakistan border. Insurgent attacks in that region increased last year even as they declined substantially in the south.

The U.S. and its NATO allies expect to put more emphasis this year on shifting to a support role after a decade of combat, with Afghan forces taking a more prominent role, especially in the south. In the eastern provinces, a lot of tough fighting is still in the offing.

“We can’t take our foot off the throat of the insurgency,” the 1st Infantry’s commanding general, Maj. Gen. William Mayville, said in an Associated Press interview Monday at his headquarters on Custer Hill, overlooking this sprawling post on the banks of the Kansas River.

Mayville and his team will be arriving in Afghanistan at an especially tense time, following Afghan outrage over what American officials call the accidental burning of Muslim holy books last month and the massacre of 16 Afghan civilians March 11, allegedly by a U.S. soldier, Staff Sgt. Robert Bales.

Mayville, an Iraq war veteran who is one of the Army’s most experienced Afghanistan hands, said the key to success is ensuring that sufficiently trained Afghan security forces — both army and police — are connected to an adequately capable Afghan government. He said he is encouraged by what he believes is a growing pool of capable and committed Afghan military leaders.

“None of this works if you then can’t connect all of this progress to the efforts to build a viable Afghan government at the local, provincial and national level,” he said.

Without commenting on the shootings or the Quran burnings, Mayville said he believes the U.S. and its allies will stick to their current strategy even as President Hamid Karzai pushes for an early end to the presence of foreign forces in Afghan villages. Mayville’s view has been echoed by numerous military and administration officials, including President Barack Obama, even though a majority of Americans say it’s time to leave Afghanistan after 10 years.

“I don’t see us coming off of this campaign plan,” he said. “And I don’t see anything where the trajectory of our campaign necessarily has been altered or changed.”

The top American commander in Afghanistan, Marine Gen. John Allen, is due to open three days of congressional testimony Tuesday. He is expected to face tough questions from lawmakers on the implications of recent U.S. setbacks and on Karzai’s demand for a pullout from rural areas. Since Feb. 1, seven U.S. servicemen have been killed by their Afghan allies.

Mayville’s task in the eastern sector is complicated by the makeup of an insurgency that is more diverse than in the Pashtun-dominated south.

“The east is the most complex area of all the battle spaces” in Afghanistan, Mayville said.

To prepare for that, the 1st Infantry’s headquarters staff, numbering about 700 people, has undergone a grueling series of exercises meant to familiarize them with not only the forces they will be commanding but also the political, cultural and social factors they will face. The headquarters spent a year in southern Iraq, returning to Fort Riley in January 2011, but has never deployed to Afghanistan.

“We had to wrap our heads around a different country, a different people,” said Lt. Col. Patrick Proctor, the division’s chief of plans. As part of that effort, key officers on the division headquarters staff visited Afghanistan in September, October and December to be briefed by U.S. and Afghan officers and get a better lay of the land. Proctor and Mayville made a final visit last week.

Adapting will be less difficult for Mayville, a 1982 graduate of West Point who parachuted into northern Iraq in March 2003 as commander of the 173rd Airborne Brigade and has spent a total of more than four years in combat since then. He has served three times in Afghanistan, most recently in 2009-10 as operations chief for Gen. Stanley McChrystal when he was the top commander there.

In his sector of Afghanistan, known as Regional Command-East, Mayville will lead five U.S. ground combat brigades, plus one Polish brigade, one French brigade and one U.S. Army combat aviation brigade. In all he’ll command about 30,000 troops, although it is possible he will lose some during the course of the year. Details of the 2012 U.S. drawdown plan have not yet been announced.

As required by President Barack Obama, the total U.S. force in Afghanistan of 90,000 troops is to be reduced to 68,000 by the end of the summer. Much of that will be achieved by reductions in Helmand province, where U.S. Marines already are handing over to Afghan forces and where the Taliban has been dealt a severe blow. It’s not clear what changes will be made to the size and mix of forces in the east.

The 1st Infantry Division, nicknamed the “Big Red One,” dates to World War I and has fought in every major American war since.