Memorial Day signals the start of a lazy summer for some, but for President Clinton it spells the end of an unusually cloistered vacation and the countdown to two major decisions: whether his wife will run for the Senate and how to deal with Slobodan Milosevic's Serbian forces that remain in Kosovo despite 10 weeks of NATO airstrikes.

After barely showing his face during the first couple's five-day vacation, which ended here tonight, the usually gregarious president plunges back into a busy schedule, including a major trip to Europe. There and at home he will face growing pressures to explain what the allies will do if Yugoslav troops continue to absorb the bombing in Yugoslavia.

Meanwhile, Hillary Rodham Clinton cannot wait much longer to state officially whether she will seek the open Senate seat from New York in 2000.

Next Thursday features the types of events likely to focus the attention of the White House and the public on these two decisions. The president is scheduled to meet that afternoon with his military advisory panel, the Joint Chiefs of Staff, which is struggling with the question of when and whether to send ground troops into Kosovo. A few hours later he and his wife will host a White House reception for graduates of Wellesley College, where alumna Hillary Clinton surely will be the center of attention.

"The vacation for him was about getting some rest, recharging the batteries, because we've got several big weeks ahead," White House press secretary Joe Lockhart said today. In addition to coping with major foreign policy decisions, he said, the president will outline new Medicare proposals in the coming days.

This week will focus largely on military themes. The president lays a wreath and makes a Memorial Day speech at Arlington Cemetery on Monday. On Wednesday he delivers the commencement address at the Air Force Academy in Colorado, a likely venue for remarks on Kosovo and other military issues.

But the biggest showdown on the Balkans may occur in mid-June, when Clinton embarks on an eight-day trip to Europe. Built around the June 18-20 summit in Cologne of the so-called Group of 8--the seven major industrialized nations plus Russia--the trip ostensibly will focus on economic matters. But Kosovo appears destined to dominate it, given the increasing divisions within NATO over whether to ease the bombing, remain on course or introduce ground forces.

The summit will include NATO's most hawkish leader--British Prime Minister Tony Blair--as well as Russian President Boris Yeltsin, who has demanded that NATO stop the airstrikes, ominously warning of dangerous breaches in East-West relations. Clinton also plans to visit Geneva, Paris, Bonn and Slovenia, and aides say he may add a tour of a refugee camp for ethnic Albanians driven from Kosovo.

With time ticking down on big decisions, the Clintons spent a remarkably quiet, low-key vacation here. The garrulous president usually ventures out for golf, shopping or handshaking when he vacations, as he did three months ago in Utah and last summer in Martha's Vineyard.

Here, however, he never set foot off the secluded 7,500-acre White Oak Plantation. The only glimpse reporters got of him was on Thursday, when he came to the compound's gate to read a brief statement about Milosevic for the TV cameras. He took no questions but quickly disappeared back into the wildlife preserve that features rhinos, lions and tigers plus a nine-hole golf course where he played several rounds with local pros.

Staffers offered few details on how much time the Clintons spent together, although Lockhart said the president cooked dinner for his wife the first night here. The president brought five books with him, and Hillary Clinton spent at least some of her time telephoning New York Democratic Party activists.

Lockhart said the president had no outside visitors until Saturday, when several Democratic advisers and strategists began arriving for today's private session on the centrist political approach dubbed the "Third Way."

They included Al From, head of the Democratic Leadership Council; White House domestic policy adviser Bruce Reed; White House communications adviser Sidney Blumenthal; former White House communications director Donald A. Baer; Rep. Calvin M. Dooley (D-Calif.); presidential pollster Mark Penn; Alfred A. Checchi, former board chairman of Northwest Airlines and former California Senate candidate; David Milliband, a top adviser to Blair; Anthony Giddens, director of the London School of Economics; Will Marshall, president of the Progressive Policy Institute; and Bob Burkett, a California lawyer and Democratic fund-raiser.