Washington — A few years ago, military recruiting ads pleaded that ''the Army wants to join you.'' Now, the word from Uncle Sam is: ''You'll do more before sunrise than most people do all day.''
The tone is one of challenge, not accommodation, and with good reason. The armed services can afford to be a lot more choosy about the men and women they sign up.
The military services are breaking records in recruiting and retention, as well as the quality of men and women in uniform, according to 1984 Pentagon figures.
The Army, Navy, Air Force, and Marine Corps are all meeting or exceeding their recruiting goals, and reenlistment rates for both first-termers and career personnel are holding steady at historically high rates as well.
While only 68 percent of new recruits had high school diplomas just four years ago, 93 percent have them today. This is well above the national youth average of 75 percent. The number of ''weekend warriors'' joining the reserves (which dropped sharply in the late 1970s) is also at an all-time high.
''Quite frankly, I'm astounded by the progress we've made,'' says Assistant Defense Secretary Lawrence Korb, the Pentagon's manpower chief.
The Reagan administration is trumpeting this good news about the US armed forces, and it hustled to get it out on the eve of the presidential election. Last year, the annual report on military manpower wasn't released until the end of November.
But it appears that the administration can legitimately take some credit here , since the positive trends are continuing despite the economic upturn that many analysts said would mean tougher times for military recruiters.
The lag in the economy early in Reagan's first term undoubtedly impelled many young men and women to sign up for military service. But figures show that recruiters did just about as well in areas of relatively high employment as they did in communities where auto plants and steel mills shut down. Increased pay for servicemen - especially the 14 percent raise in 1981 - has helped here. The improvements also may reflect a general return to patriotism as well.
While today's news on recruiting and retention may be rosy for the Pentagon, there are indications that the long-term picture is clouded.
''There are good reasons to ask whether the successes of the early 1980s can be sustained, given the prospect that the military could run up against an adverse supply-and-demand situation later in the decade,'' Martin Binkin of the Brookings Institution warned earlier this year.
He was referring here to the projected drop in the ''youth cohort,'' those 18 -to-26 year-olds targeted for recruitment. With the end of the ''baby boom,'' this segment of the population will decline 16 percent over the next decade.
In a report for the more conservative Heritage Foundation, Lt. Col. Robert K. Griffith, a US Army historian, said experience during prior economic recoveries ''suggests that quality of enlistments will fall off and reenlistments, especially among highly-skilled personnel, will also decline.''
He noted that the Army, early in 1984, reported a 22 percent drop over the previous year in the number of above average young men (those scoring higher on military tests) who inquired about enlistment.
Over the past four years, the Reagan administration has increased the active-duty force by about 80,000 to 2.1 million. It would like to see that figure rise another 50,000 overall, and will seek an additional 30,000 in the coming fiscal year. Congress may cut those figures.
While pay increases have helped boost the Pentagon budget, the cost has been offset by the larger number of high school graduates and by more reenlistments. Graduates are much less likely to drop out, and retaining service personnel means fewer have to be taught basic skills.
The services figure they have to recruit six men or women for every one who sticks it out for a full career. In fact, says Mr. Korb, the armed forces are facing ''promotion humps'' in some skill categories because of the high-retention rate.
Some critics say that minorities, especially blacks, are overrepresented in the all-volunteer force. While blacks comprise 13 percent of the 18-to-24 year-old population, they account for 18 percent of the military and 23 percent of the Army. When other minorities are added in, the total is 25 percent of the services compared with 23 percent of the youth population.
While the Reagan administration has cut back the goals of the Carter administration for adding more women to the force, the overall numbers of women in uniform now are the highest since the end of World War II. There are 203,000 women in the armed forces today, which is 9.5 percent of the total. Ten years ago, women were just 3 percent of those in service. Percentage of new recruits with high school diplomas
'80 '81 '82 '83 '84 Army 54 80 86 88 91 Navy 75 76 79 91 93 Marine Corps. 78 80 85 92 95 Air Force 83 88 94 98 99 Total Defense Dept. 68 81 86 91 93 SHIRLEY HORN - STAFF