THE PLAYERS An alliance formed in 1949 to deter Soviet aggression. The central principle is that an attack in Europe or North America against any member is an attack against all. The alliance has grown to 28 member nations, ranging from the U.S., Britain, France and Germany to former Soviet countries like the Czech Republic, Hungary and Poland. Albania and Croatia are the newest members. AFGHANISTAN The summit will affirm the shift in NATO’s military mission in Afghanistan from a combat role to an advisory role next year, and on plans to help underwrite the Afghan military after the NATO-led military mission ends two years from now. NATO is pledging to maintain a multinational combat force in Afghanistan until sometime in 2014, with a firm deadline to end the mission by 2015. NATO nations, along with others such as Australia that participate in the NATO-led mission, have planned a gradual withdrawal of combat forces ahead of that deadline. The election of Socialist President Francois Hollande in France complicates that agenda. Hollande campaigned on a promise to pull French troops out of Afghanistan by the end of this year – two years early. The summit will also showcase efforts to get firm financial commitments for support of Afghan forces. NATO argues that even the projected bill of about $4 billion annually is cheaper than the cost of war. NATO MODERNIZATION Most alliance members have endured economic reversals that make any major new defense spending unappealing or impossible. The alliance is laboring under the weight of outdated or incompatible equipment, and suffers major gaps in military capability that the better-equipped and better-funded U.S. military often has to fill. Some of those shortfalls were on display in last year’s successful NATO air mission in Libya. Former Defense Secretary Robert Gates rattled NATO when he said the alliance risked falling apart if it continued to leave the hardest fighting and biggest bills to the U.S. MISSILE DEFENSE The alliance will declare it has partly completed a missile defense shield for Europe. The system has achieved “interim capability,” against possible missile threats from Iran or elsewhere, NATO claims. Russia opposes the system, and has rebuffed NATO efforts to form a partnership.