I agree with Mark Shields that it is important for President George Bush to define and explain American goals in the Persian Gulf {"What Are the Boys Fighting for?" op-ed, Aug. 28}. I believe, however, that the president has done an adequate job of this through the first month of the crisis. Clearly, the longer American forces are in the region, and the longer Saddam Hussein remains in Kuwait, the more difficult it is for the president to maintain America's focus on the goals that he articulated at the start of the crisis.

It also was important that Mr. Shields pointed out the inequality in the burden of actual fighting that could characterize a war in the Persian Gulf, as it did the war in Vietnam.

Thirteen years ago, I returned home after having served six years on active duty as a U.S. Army officer, at least part of the time as an infantry platoon leader, although not in Vietnam. At a conference in Berlin, I was approached by a Harvard University classmate who told me in very direct language that he too had contemplated serving on active duty during the Vietnam War, but he was now making a very real sacrifice every bit as large as it would have been had he served in uniform.

My friend explained that he had just been appointed to a high-level political post in the Carter administration, and since he had just graduated from a prestigious business school, he admitted that he was giving up a six-figure income and sacrificing the amenities of life that go with it, including perhaps a summer place in Nantucket or elsewhere. I politely commended him for his willingness to serve his president, but also disagreed with his comparison.

Whatever happens in the Gulf, I hope that most Americans will come to understand and appreciate the enormous sacrifice and risks that are undertaken by men and women in uniform today. I also hope they understand that the unique commitment and sacrifice that are asked of these men and women are asked of almost no other servants of our government. ROGER A. BROOKS Bethesda