In Shadow of ‘Brexit,’ NATO Will Sound Message of Unity Against Russia

But now that this is actually expected to happen during NATO’s two-day gathering here this week, the question is whether — with Britain’s startling exit from the European Union sucking up all the political oxygen — anyone will even notice.

“Militarily, this summit will be about strengthening forces along the eastern front,” said Michal Baranowski, director of the Warsaw office of the German Marshall Fund. “Politically, it’s a Brexit summit.”

The gathering here on Friday and Saturday — drawing every major leader in the trans-Atlantic alliance, including President Obama, Prime Minister David Cameron of Britain and Chancellor Angela Merkel of Germany — will be the largest NATO summit meeting in history, with 28 delegations from European Union countries, 26 from other nations, and representatives from the United Nations and the World Bank.

Much of what is expected to be adopted has already been agreed upon in earlier meetings of foreign and defense ministers — “It is pre-cooked,” as Mr. Baranowski put it — so attention is likely to focus instead on how alliance members, including Britain, make an ostentatious show of Western unity despite the shadow of “Brexit” and the weakening of the European Union.

“NATO is the last European institution standing, and it is the main link between Europe and North America,” said Jakub Grygiel, a professor of international studies at Johns Hopkins University and a senior fellow in residence at the Center for European Policy Analysis. “Hence, NATO is likely to become more important as the E.U. weakens, because it will continue to serve as a mechanism of coordination and cooperation.”

Under an agreement expected to be ratified at the summit meeting, four battalions of 800 to 1,200 troops each would be stationed in countries bordering Russia in what is being called a “persistent rotation” that makes the NATO presence essentially permanent; each multinational battalion will be in position for six months, but will not depart before replacements have arrived.

Britain has agreed to take command of a battalion to be based in Estonia and Germany and placed in Lithuania. It is expected that the United States will not only command the troops, but also make up the bulk in a force to be stationed in Poland.

While NATO struggled for months to find a country to take command of the fourth battalion, to be based in Latvia, Canada is now widely expected to emerge during the summit meeting as that group’s leader.

“Since 1999, when Poland joined NATO, this is the most important summit for us,” said Tomasz Szatkowski, Poland’s deputy minister of defense. “It provides for the actual presence of Western allies in Poland.”

In addition, under the plan agreed to in advance of the summit meeting, an entire brigade comprising four more battalions would operate on a roaming basis throughout the front line from the Baltics to Bulgaria — though the details, including where such a force would be based, remain to be hammered out.

Of course, another topic sure to be discussed is the American presidential election campaign, in which the presumptive Republican nominee, Donald J. Trump, has expressed doubts about the continued need for NATO and questioned whether the United States was being properly compensated for the military forces it has stationed across the globe.

“I can’t imagine anyone will say it publicly, but I cannot imagine it will not be part of the private discussions,” Mr. Baranowski said. “A world with both Brexit and Trump? Holy moley, hold onto your pants.”

At the previous NATO summit meeting in Wales in 2014, not long after Russia’s seizure of Crimea, the alliance announced the creation of a new rapid-reaction force that could move swiftly into a threatened region and, using previously positioned caches of weapons and equipment, delay an invading force until full NATO forces could arrive.

But with Russia’s continued belligerence, front-line governments, spearheaded by Poland and the Baltic States, pushed for a more robust posture this time around.

What they are getting, while below their fondest hopes, does elevate NATO’s strategy to what is being called “enhanced forward presence.”

“It’s been described as a speed bump,” Mr. Baranowski said. “But what it does is raise the price for the Russians.”

The Russians would still have a massive advantage in troops — five or six times the number — and weaponry. But any incursion into the Baltics or Poland would put the Russian military in immediate contact with multinational NATO troops.

Polish officials have said they would have preferred a larger NATO force, but are content with this for the time being. “This is a good compromise between what is desirable and what is possible,” Mr. Szatkowski said.

With some NATO states preferring a more diplomacy-based approach toward Russia and several countries still balking at financing the alliance at the agreed-upon level, this was as far as the front-line states felt they could push.

“What Poland needs and what is realistic to expect are different things,” said Roman Kuzniar, a professor at the Institute of International Relations at the University of Warsaw and a former adviser to the president on foreign affairs under a previous government. “The figures are fairly symbolic but, obviously, it is very important that these troops will be here.”

How to enhance forces along what is being called the “southern flank,” in response to the terrorism threat from the Middle East and the massive migrant wave from the region, will also be discussed at the summit, as will concerns about Russia’s development of low-yield, tactical nuclear weapons.

While the NATO meeting is the reason for the Warsaw gathering, other meetings will occur here over those two days. Senior European Union and NATO officials will get together, as will union leaders and American officials.

“Usually, that E.U.-U.S. meeting at these summits is fairly low key,” Mr. Baranowski said. “But now, because of Brexit, it’s a much bigger deal.”

The larger question, Mr. Kuzniar said, is how Poland and other front-line states will respond to this “new strategic reality,” with NATO troops stationed in their territory, though not in the numbers they desired.

“Will they develop more effective territorial defense forces and capabilities of their own?” he asked. “Will they seek offensive weapons to threaten Russian assets? Or will they accommodate Russia in some form?”