Warsaw just made the biggest bet on European integration since Maastricht - and it's one that could reshape the entire EU's institutional architecture.

Poland's Finance Minister Andrzej Domański has publicly endorsed Germany's proposal for an "E6" core group of EU member states to fast-track integration on critical economic policies, including the long-stalled Capital Market Union.

The E6 - shorthand for the six largest eurozone economies: Germany, France, Italy, Spain, the Netherlands, and now Poland - would form an inner circle empowered to move ahead on integration projects without waiting for unanimous agreement from all 27 member states.

Brussels decides more than you think. This proposal could create a two-speed Europe by design, not by accident.

"We need mechanisms that allow willing member states to move forward," Domański said in remarks captured on video. "The Capital Market Union has been discussed for a decade. It's time to build it."

The Capital Market Union - EU jargon for integrating Europe's fragmented financial markets - has been a Brussels pipe dream since 2015. The idea: make it as easy for a Portuguese startup to raise money in Frankfurt as in Lisbon, or for a Dutch pension fund to invest in Italian infrastructure without navigating 27 different regulatory regimes.

Progress has been glacial. Enter the E6.

Poland's support is the geopolitical earthquake here. Just two years ago, Warsaw was locked in a rule-of-law battle with Brussels that saw €36 billion in EU funds frozen. The previous government, led by the nationalist Law and Justice party, routinely vetoed EU integration proposals and positioned Poland as a brake on Brussels centralization.

Now, under Prime Minister Donald Tusk's pro-European coalition, Poland is volunteering to join the EU's core.

The shift reflects Warsaw's new calculus: with the United States under Donald Trump signaling retreat from European security commitments, Poland needs a stronger, more integrated EU - particularly on defense and economic resilience against Russia.

But the E6 proposal raises profound questions for the other 21 member states. What happens to Ireland, whose tech-driven economy depends on cross-border capital flows? Or Sweden and Denmark, which have historically punched above their weight in EU financial regulation? Or the smaller Eastern European states that fought for decades to join the EU, only to find themselves relegated to a second tier?

Brussels has tried multi-speed integration before. The Eurozone itself is a two-tier system - 20 countries use the euro, seven don't. Schengen has its own boundaries. Enhanced cooperation mechanisms exist in EU law precisely to allow subsets of countries to move ahead.

But those were opt-in projects. The E6 risks becoming an opt-out reality for everyone else.

Critics point to the European Banking Union, launched after the 2008 financial crisis with similar promises of streamlined decision-making. A decade later, it remains incomplete, paralyzed by Franco-German disagreements over deposit insurance.

If six countries can't agree, the logic goes, what makes anyone think they'll succeed where 27 failed?

The counterargument: six is better than 27 precisely because it eliminates the veto points. Hungary's Viktor Orbán has used unanimity voting to extract concessions and delay EU action for years. An E6 that doesn't include Budapest is an E6 that can actually function.

That's the unspoken subtext of the proposal - it's not just about speed, it's about circumventing obstructionists.

The European Commission, officially neutral, has blessed the concept in careful bureaucratese. "We support all efforts by member states to deepen integration within the framework of the Treaties," a spokesperson said.

Translation: go ahead, but don't break EU law doing it.

The Capital Market Union is the test case. If the E6 can actually deliver a functioning cross-border capital market - harmonized securities rules, integrated clearinghouses, unified insolvency law - it would be the biggest single-market achievement since the euro.

If it collapses in Franco-German squabbling or gets bogged down in technical details, it will prove that the problem isn't 27 vetoes, it's the fundamental difficulty of integrating 27 different legal, tax, and regulatory systems.

For London, this matters. Post-Brexit Britain still does more financial business with the EU than any single member state. A Capital Market Union that excludes the City would reshape global finance. A Capital Market Union that includes the City - via some form of regulatory alignment - would reshape Brexit.

For Lagos or Los Angeles, the question is whether Europe can build capital markets deep enough to compete with Wall Street or the City. Right now, European companies raise money in New York because European markets are too small and fragmented. An E6 that fixes that becomes a geopolitical player.

Poland's Finance Minister ended his remarks with a line that would make Brussels federalists weep with joy: "We must have the courage to build a stronger Europe."

Courage, or desperation? With Russia on the warpath, America turning inward, and China outspending Europe on everything from AI to infrastructure, the EU's crisis of relevance is existential.

The E6 is a bet that a smaller, faster core can save the whole. Whether the other 21 see it as salvation or betrayal will define European politics for the next decade.

Brussels decides more than you think - but soon, it might be six capitals doing the deciding.