WASHINGTON, D.C. — The Army is significantly cutting the total number of soldiers it expects to have in the force over the next two years, as the U.S. military faces what a top general called “unprecedented challenges” in bringing in recruits. Army officials said the service will fall about 10,000 soldiers short of its planned end strength for this fiscal year, and prospects for next year are grimmer. Army Gen. Joseph Martin, vice chief of staff for the Army, said it is projecting it will have a total force of 466,400 this year, down from the expected 476,000. And the…