BERLIN // Bitter foes for centuries, Germany and France now rarely miss an opportunity to profess their close friendship, so tomorrow's ceremony in Berlin to mark the 50th anniversary of the Elysée Treaty that sealed their alliance promises to be a veritable lovefest.
But, in truth, the relationship is beset by deep differences in core areas such as the euro crisis and security. Germany's tepid offer of two transport aircraft to help France, its closest ally, fight Islamist militants in Mali is the latest example of how far removed their official declarations of unshakeable solidarity are from reality.
Another was last year's collapse of merger talks between European defence giant EADS and British Aerospace, which was attributed in part to mutual suspicions between France and Germany. And when France, Britain, the US and Gulf allies intervened in the Libyan conflict in 2011, Germany stood on the sidelines, even abstaining in the UN Security Council vote.
"Mali is the third instance in a row where this gap between aspiration and reality has become visible. The rift goes through all aspects of French-German relations," Ulrike Guérot, an analyst at the European Council on Foreign Relations, a pan-European think tank, said.
Part of the problem is that Germany is clearly the dominant partner. Its increased political might since unification in 1990 has upset the equilibrium between them.
"During the Cold War, there was a balance with the Germans assuming economic leadership and leaving political leadership to the French," Sabine von Oppeln, a political scientist at Berlin's Free University, said. "But since unification, the Germans have gained political weight and haven't lost their economic leadership."
The difference has become increasingly evident during the euro crisis that has left France grappling with weak growth and high unemployment, while Germany has been powering ahead thanks to an industrial sector invigorated by labour market reforms that France has yet to tackle.
Many in France balk at the prospect of emulating the successful German economic model, which is fundamentally different from their own.
The gulf between German and French economic policy traditions - the former focusing on spending restraint and the latter on state intervention - has widened since the socialist Francois Hollande was elected France's president last year.
Mr Hollande has openly criticised the German chancellor Angela Merkel's insistence on austerity to overcome the euro crisis, and said more growth-orientated measures were needed to help the debt-laden countries of southern Europe.
Politicians will brush aside these problems in their speeches tomorrow. The German and French cabinets and MPs from the two countries will congregate in the Reichstag parliament building to celebrate the treaty forged in 1963 by President Charles de Gaulle and Konrad Adenauer, the West German chancellor.
The agreement, aimed at reconciling the nations after the world wars, launched an array of joint initiatives and enshrined regular government meetings which since 2001 take place every six to eight weeks.
Even though Mr Hollande declared he was "completely satisfied" with the German offer of help for Maili, one of his cabinet ministers, Alain Vidalies, complained last week that logistical aid from other European countries had been "somewhat minimal … with some regrettable absences".
It was a veiled reference to Germany, which only decided on Wednesday to supply two Transall transport planes to fly West African troops to Mali's capital, Bamako.
The festivities in Berlin will focus on the historic rapprochement between the two nations, and on their achievements: the European single market, the EU itself and the euro would have been unthinkable without the Franco-German alliance.
"It's always been a marriage of convenience," said Ms von Oppeln. "Both countries know that they depend on the success of the EU and that they can't master the challenges of the present on their own."
Recent surveys show that a majority of French and Germans no longer view each other through the prism of war. But a cultural divide remains between the land of fine wine and haute cuisine and the land of beer and sausage.
According to a survey by the French Ifop institute, the first word French people think of when asked about Germany is "Merkel", followed by "beer", "car", "strict", "sausage" and "sauerkraut."
The Germans had a far more romantic image of France, associating it with "Paris", followed by the "Eiffel Tower", "wine" and "baguette," the survey showed.
"Really great things have been achieved if you look at where we were in 1913 and 1963," said Ms Guérot . "There's a new normality and ease in discussions. We've always had rows, and they've been a creative driving force in the relationship."
Paradoxically, European integration tended to make most progress when France and Germany had a public row and then settled their differences, said Ms Guérot. "The resulting compromise has always been more acceptable to the other EU states. Whenever Germany and France have formed too much of a common front, it's been bad because it has pitted them against the rest of Europe."