Foreign and military policy has not been central to the presidential campaign so far. One reason is that polls show those issues are not high on the voters' priority list. Another factor is that the disagreements between Gov. George W. Bush and Vice President Al Gore on foreign and military policy are subtle compared with the fundamental contrasts in their approaches to Social Security, education vouchers, tax cuts and abortion. But the differences are there and could lead to big changes in how U.S. power and influence will be deployed on the world stage, depending on who wins the election.

For example:

Republican Bush and Democrat Gore both say they want to build a missile defense system. But Bush's is much more ambitious, and he sounds determined to build it no matter the cost. Gore favors a minimalist system and reserves the right to call the whole thing off if the damage to various bilateral relationships and the arms-control environment seems too dire. Gore and Bush both reject isolationism and say the United States must remain the world's leader. But Gore is much more of a multilateralist, willing to accommodate the United Nations and other international organizations. Bush is more of a unilateralist, less interested in balancing U.S. interests against the international community.

Bush and Gore agree that the United States cannot be the world's policeman. But Gore's record and his key foreign policy concept, which he calls "forward engagement," suggest that he would be quicker to send U.S. troops into situations where the problem is moral, such as promoting democracy or stopping genocide. Bush wants to restore the doctrine that you use troops to defend U.S. territory, allies or vital resources, such as oil. The differences may be in the details, but they could turn out to be very significant differences," said political scientist Andrew Latham of Macalester College in St. Paul, who specializes in international security issues.

From the U.S. entry into World War II in 1941 until the fall of the Berlin Wall in 1989, foreign and military issues were at or near the top of issues voters cared about, and the voters elected a succession of military veterans, many of them war heroes. But the end of the Cold War seems to have ended the primacy of such issues in presidential politics. President Clinton, who avoided the Vietnam-era draft, has defeated two war heroes, George Bush the elder and Bob Dole, in the two post-Cold War presidential elections. He did it by emphasizing the economy and a raft of other domestic issues.

A September ABC/Washington Post poll asked registered voters to indicate the issues that would be "very important" to them in deciding how to vote in the 2000 presidential election. Defense and foreign policy ranked 11^th and 13^th, respectively. The top 10 were all domestic issues. When Bruce Jentleson, a Gore foreign policy adviser, and Richard Haass, a Republican foreign policy expert, came to Minneapolis in May for a forum on foreign policy and campaign 2000, they agreed that foreign policy should be an important element in any presidential campaign, since it inevitably becomes an important part of every presidency and is one of the few areas where presidents can act unilaterally. But they acknowledged that because of a lack of interest by voters, foreign policy would not get the attention domestic issues would, unless the campaign year produced an unexpected foreign policy crisis to which the candidates would be forced to react. So far that hasn't happened.

Bush and Gore have not ignored foreign policy and military issues. Each has given several speeches on those themes. But neither campaign has paid foreign or military policy the ultimate compliment, in a presidential campaign, of unleashing a television commercial on the topic. Bush wants to increase defense spending. So does Gore. Gore favored permanent normal trade relations with China and China's admission into the World Trade Organization. Ditto Bush. Both oppose lifting sanctions against Iraq or normalizing relations with Cuba.

The major-party nominees are not identical on these or other foreign and military issues. But to understand their differences, you have to pay attention to their tone and emphasis. Here are examples of differences that are less than concrete but potentially significant:

Bush has criticized Clinton and Gore for "sending our military on vague, aimless and endless deployments." He says the United States should not use troops to intervene in other nations' civil wars, or to stop campaigns of ethnic cleansing, unless the situations threaten vital U.S. interests. Political scientist Robert Packer of Carleton College in Northfield, Minn., an international security affairs specialist, said Bush defines those interests in a traditional way: protection of the homeland, survival of key allies and defense of vital resources, such as oil.

Bush has said that long-term peacekeeping missions are not the best use of U.S. troops and that such responsibilities should be passed along to U.S. allies. His administration would conduct "an immediate review" of U.S. missions in "dozens of countries," with an eye to ending some and bringing home the troops. Gore, on the other hand, says in the summary of his foreign policy views on his Web site that "he has stood up for American values by supporting military intervention to end ethnic cleansing and by promoting democracy, human rights and the rule of law." The key word in that phrase is "values." Gore argues that some situations are so offensive to American values that they justify intervention even if they do not meet a traditional definition of vital national interests. Gore pushed for all three of the major military interventions begun under Clinton _ in Haiti, which was justified as an operation to restore democracy, and in Bosnia and Kosovo, which were justified as efforts to end ethnic cleansing.

Gore uses the phrase "forward engagement" to characterize his foreign and military policy. It means that the United States should sometimes intervene early and try to solve the root causes of international problems before they turn into full-blown crises. Jentleson, the Gore adviser, says that Bush is insufficiently attentive to what he calls "new agenda" items that are expanding the old definition of U.S. interests to include environmental, moral and even health issues, such as the AIDS epidemic in Africa.

All of these comments seem to imply that Bush disapproves of the Clinton interventions and that he would bring home the thousands of U.S. peacekeeping troops stationed in Bosnia and Kosovo and not get involved in future cases where the main justification is U.S. "values," while Gore would be likely to use the U.S. military for nontraditional missions. The trouble is that Bush supported, however reluctantly, the Kosovo bombing mission and has stopped short of specifying that he would bring troops home from there or Bosnia on any concrete timetable. There is no specific international situation on which Bush and Gore differ openly about whether U.S. troops belong there. Packer said that despite the lack of concrete disputes, Bush and Gore would bring fundamentally different approaches to the question of when to use U.S. troops.

"After Kosovo, the Clinton administration set up the Clinton Doctrine, which said that the United States reserves the right, with its allies, to multilaterally intervene in the internal affairs of sovereign states," Packer said. "Gore would continue that doctrine. Bush, although he hasn't said so explicitly, will shy away from that doctrine". "You can tell this in part from the people Bush has around him, such as General Colin Powell, who might be secretary state if Bush wins the election," Packer said. "Powell developed his own doctrine, the Powell Doctrine, which set a high barrier for U.S. intervention. He said there has to be a clear U.S. national interest at stake, an achievable military objective and an exit strategy."

Bush has argued that because of the inattention and misplaced priorities of the Clinton administration, "the next president will inherit a military in decline." Bush has promised to rebuild the military's strength and morale and promised to spend $1 billion a year on raising military pay. Gore disputes that the military is declining. The military has been reduced in size since the end of the Cold War, but Gore's surrogates have enjoyed pointing out that the downsizing began when Bush's father was president and Bush's running mate, Dick Cheney, was secretary of defense.

But Gore has also proposed to increase military spending. In fact, although Bush has spent more rhetoric on the state of the military, Gore has proposed a larger increase _ $100 billion over the next 10 years _ compared with the $45 billion that Bush committed in his fiscal blueprint to increased military spending.

The Clinton administration has been developing what is usually described as a minimalist system to intercept incoming missiles that might be fired at the United States from one of the so-called rogue states: Iraq, Iran, Libya and North Korea. It would be based in Alaska. Its goal would be to have 20 interceptors deployable in 2005 and 200 in 2010. Russia is opposed to the project, which it says would violate the 1972 Anti-Ballistic Missile (ABM) treaty. China also has objected to the project, although it is not a party to the ABM treaty. Many analysts worry that deployment of the system would spur China to expand its own missile program.

After the system failed a test in July, Clinton announced in September that he would leave to the next president the decision whether to proceed with deployment. Bush and Gore say they want to proceed. Both say they would try to reassure the Russians that the system is no threat to them and persuade Russia to modify the ABM treaty. But missile defense is an area where differences in tone and emphasis may indicate big differences _ although they are hard to specify now _ in what the two candidates would do as president. For example, Bush describes the system he wants to build as "robust" and "based on the best available options at the earliest possible date," all of which seems to be code for a more ambitious program built on a faster schedule than Clinton and Gore have in mind and for Bush going ahead with it no matter the objections of Russia or China.

The Washington-based Center for Strategic and International Studies has estimated that a system meeting Bush's goals would have to involve interceptors based on Navy ships or possibly in space, compared with the land-based system now on the drawing board, and would cost $100 billion to $120 billion, compared with the $30 billion to $60 billion estimated cost for the Clinton program. Bush has not put any money aside in his fiscal blueprint for the more ambitious program. Gore's statements on missile defense are technically similar to Bush's but miles apart in tone. While Bush wants to proceed as soon as possible, Gore said he was glad Clinton's postponement would provide more time to test the technology before deciding whether to deploy. He has shown no interest in the space- or sea-based versions.

Like Bush, Gore says he would proceed with missile defense _ if he decided it was workable, affordable and necessary _ even if he failed to persuade the Russians to amend the ABM treaty. But he said he would also "look for very creative approaches for joint U.S.-Russian responses to a threat that can be aimed at either one or both of us." By contrast, Bush says his attitude toward joint programs with Russia "would depend on how Russia behaves."

Bush's greater willingness to scrap the ABM treaty if it gets in the way of missile defense, and Gore's greater desire to preserve the treaty, is an example of why many analysts describe Gore as a multilateralist and Bush as a unilateralist. "In a number of areas," Latham said, "Bush is saying that the U.S. should act as it sees fit in its own national interest, without necessarily worrying too much about the feelings of either its allies or Russia and China. If they don't like it, too bad." Gore wants the United States to pay the dues that it owes the United Nations; Bush says only if the United Nations reforms its bureaucracy and revises the dues formula to reduce what he calls "America's disproportionate share."

When the Senate in 1999 rejected the Comprehensive Test Ban Treaty, which would establish a permanent ban on the testing of nuclear weapons, Bush agreed with the opponents that the treaty was unverifiable and would be too constraining on the United States; Gore called it an act of "massive irresponsibility" and promised to push for ratification if he becomes president. Gore also favors and Bush opposes ratification of the Kyoto Protocol, which would require the United States to reduce industrial emissions that contribute to global warming.