The fierce rivalry between the European Commission and European Council roared back to life this week, as the institutions tussled over an ambitious package of measures on the future of the single currency.

The Council pre-emptively dismissed the package — branded a "roadmap for deepening Europe's Economic and Monetary Union" — as an unhelpful overreach on fiscal policy, and the latest stunt in the intense, and escalating, tug-of-war for control of the EU.

"It is indeed very much about institutional interests, both in timing and substance," one senior official said, echoing a view shared throughout the 11th floor executive suite of the Council's Europa building.

The inter-institutional battle is embodied less by the two presidents — Jean-Claude Juncker and Donald Tusk — who enjoy a congenial relationship, than by their cabinet chiefs: Martin Selmayr, the famously domineering and Machiavellian German on Juncker's side, and Piotr Serafin, the low-key Polish civil servant on the side of Tusk.

The rivalry has been marked by petulance, vanity and pettiness.

Selmayr oversees a bureaucracy of some 30,000 civil servants. Serafin leads a team of just a few dozen who support Tusk's role as the convener of the 28 EU heads of state and government. But on behalf of their bosses, Selmayr and Serafin are gladiators: protecting their interests, prerogatives and public images, while simultaneously defending institutional terrain in a city where turf wars are fought every day.

Selmayr and Serafin, both trained lawyers and longtime civil servants, do not particularly like or trust each other, associates said.

Serafin regards the detail-obsessed Selmayr as someone whom EU capitals view as untrustworthy, and therefore as a source of tension and unpredictability.

Selmayr regards the e-cigarette puffing Serafin as leading an operation that's too lax, and that occasionally allows individual member countries to run amok. (Tusk and Serafin's native Poland, which is in an ongoing clash with the Commission over rule-of-law issues, ranks near the top of that list.)

The fight over fiscal policy is just the latest skirmish.

In recent months, under Selmayr's stewardship, the Commission has moved repeatedly to get ahead of the Council, or undercut Council initiatives, including at a digital summit of EU leaders in Tallinn. Juncker arrived armed with handouts detailing all of the digital policy proposals his Commission had put forward and blamed the Council for not acting on most of them.

Blueprint vs. Blueprint

At the heart of the rivalry are two competing, if nearly indistinguishable, blueprints for the future of the EU: Juncker's State of the Union speech, which he delivered in September, and Tusk's "Leaders' Agenda," which EU leaders authorized at a dinner in Tallinn on September 28 and approved at their summit in October.

There's one key difference: in the State of the Union speech, Juncker formally called for combining the Commission and Council presidencies into a single position — his own, of course.

It wasn't the first time he had raised the possibility. As Juncker and Tusk prepared to pose for a photo with U.S. President Donald Trump in May, Tusk noted, "We have two presidents in the EU." Juncker, pointing at Tusk, quickly added: "One too much."

The rivalry has been marked by petulance, vanity and pettiness, and the weapons of choice, unsurprising for a duel between top civil servants, include memos and reports by their respective legal teams.

In his State of the Union speech, Juncker called for a special summit meeting in Sibiu, Romania, to be held on March 30, 2019, the day after the U.K.'s withdrawal from the EU. Romanian President Klaus Iohannis readily agreed.

But it is the Council — not the Commission — that decides when and where EU leaders meet. And a month later, Tusk came back and announced that indeed there would be a summit in Sibiu, not on March 30 but on May 9, when the EU celebrates "Europe Day."

Immediately after the British referendum, the Council moved quickly to take the lead in managing the U.K.'s departure. But Selmayr reacted furiously to the appointment of Didier Seeuws, a veteran EU official, to lead a special task force as the Council's point-person on Brexit, calling it a "power grab" and "ridiculous move," according to EU officials. Commission lawyers argued successfully that the Commission must lead talks with the U.K., and Juncker quickly named France's Michel Barnier as the EU's chief negotiator.

Just two months later, Tusk convened a summit in Bratislava, issuing a darkly-worded invitation letter that many leaders regarded as too bleak. As a result, according to the Commission, “some leaders” asked Juncker to table a list of initiatives and deadlines for achieving them — a point that Selmayr wasn’t shy to make to a group of top aides to EU leaders in September last year, happily complying with the request in an e-mail the night before the summit with his own set of proposals.

The State of the Union speech has since been used by Selmayr as a sort of battering ram for the Commission to press forward on any of the long list of policy goals that Juncker laid out.

The slew of Commission proposals aiming to revamp the eurozone’s overall economic and monetary system unveiled on Wednesday was a classic example.

Under the plans, the eurozone’s bailout arm would become a European Monetary Fund and there would be a eurozone economy and finance minister who would simultaneously serve as a Commission vice president and chair the Eurogroup of eurozone finance ministers.

The Commission pushed forward despite clear signals that eurozone leaders did not have the appetite for drastic action. In a statement on the package Wednesday, Juncker showed no sign of apprehension. "After years of crises, it's now time to take Europe's future into our own hands," he said.

What he meant was: it's time to take Europe's future into my hands. And the Council was not about to let that happen. Maneuvering to get ahead of the Commission's formal announcement, the Council released a draft document prepared by Tusk in advance of a eurozone leaders' summit, in which he made a case for a much narrower set of goals.