A quarter century after the Iron Curtain that once divided Europe opened, the European Union nations and Russia are again involved in a tug-of-war, this time over six former Soviet Republics.

EU leaders are courting the six at a special summit in Riga that opened Thursday, offering better economic cooperation and promising financial aid and help for good government. Moscow, meanwhile, is doing what it can to keep the countries within its sphere of influence.

The same issues were at the heart of the 2013 Eastern Partnership held in Vilnius. It was at that meeting that Ukraine's then-leader, Viktor Yanukovych, abruptly decided to turn his back on the EU and embrace Moscow instead. In addition to sparking the current conflict in Ukraine, the incident refuted any notion that a re-alignment could be smooth.

The EU has since decided it needs a piecemeal approach to courting the six nations. Ukraine, Georgia and Moldova are considered closer to the fold, while Armenia, Azerbaijan and Belarus are at arm's length at best.

Here's a look at the six nations and what's at stake for each at the 2015 summit, which concludes Friday:

ARMENIA: The mountainous country stepped back from seeking an economic association deal with the EU two years ago and joined Moscow's Eurasian Economic Union early this year. It is heavily dependent on Russia, both for economic and military reasons. Still, the EU does not want to give up on the country and is seeking relations in all areas that do not overlap with its membership in the EEU. Its unresolved dispute with Azerbaijan over control of the Nagorno-Karabakh region is an impediment to closer EU relations.

AZERBAIJAN: Azerbaijan's major oil reserves and decade-long economic boom make it an attractive potential partner for the EU, which needs to diversify its energy sources away from a heavy dependence on Russian gas. The problem is that the EU also says that the rule under President Ilham Aliev has major human rights problems. Don't expect any warmth in Riga, since Aliev is one of the few leaders of the 34 nations involved who decided not to show up. Still, EU president Donald Tusk on Thursday accepted an invitation to come visit Baku as the EU seeks a new agreement with Azerbaijan after Aliev declined one offered under the terms of the Eastern Partnership.

BELARUS: The EU has long had difficult relations with Belarus, one of Moscow's closest allies, and has sanctions in place because of human rights abuses and treatment of political opponents. Yet there's a new push for a breakthrough in relations, especially after President Alexander Lukashenko has started to display more independence in his dealings with Putin. Lukashenko also improved his standing by helping to broker the Minsk cease-fire agreement in eastern Ukraine. The EU will be looking for a diplomatic opening from Lukashenko's top people in the absence of the leader himself in Riga. Nothing much can be expected in the near future, since Belarus also recently joined Moscow's EEU. In addition, Russia wields substantial "soft power" in Belarus, supplying all of its gas imports and taking nearly half of Belarus' exports.

GEORGIA: The former Soviet republic has already taken a step away from Moscow by signing an economic association agreement with the EU. Little love is lost between Russia and Georgia since the latter lost some 20 percent of its territory after the 2008 war. The EU is seeking increased ties but it is still stopping short of granting the country visa-free access. While Georgia is doggedly seeking to spin out of Russia's orbit by seeking NATO membership, Russia is applying pressure by tightening military and economic ties with Abkhazia and South Ossetia, the two regions Georgia lost in 2008.

MOLDOVA: The EU has perhaps warmed most to the small nation of Moldova, which borders EU member Romania. The two already have signed an economic association agreement and Moldova has secured visa liberalization with the EU, making it easier for residents to travel in EU countries?. Russia has a foothold in Moldova's separatist Trans-Dniester region, where some 1,500 Russian troops are deployed, but Ukraine's decision Thursday to block transit access for those troops could weaken Russia's influence.

UKRAINE: Ukraine is by far the biggest prize when it comes to economic potential and political influence, as the last 18 months of turmoil and fighting have shown. After the demise of Yanukovych, the new government has followed a pro-EU course, but has little to show for it because of the military conflict in the east and the loss of Crimea to Russia. The economy is in tatters and swathes of territory have been destroyed by fighting. The EU keeps pushing for political reform in Kiev and is promising an 11 billion euro (dollar) aid program to keep the nation afloat.