There is always a touch of kitsch in the air when an aging couple renews its vows. If they want to overcome phases of indifference and crises and reestablish their partnership in a symbolic gesture. The situation is no different for nation states. The champagne often served on such occasions quickly goes to your head, but its effect soon subsides.

In Aachen on Tuesday, Germany and France will be toasting the renewal of their partnership. And this is about more than just navel-gazing. It was always one of German foreign policy's guiding principles that the Federal Republic never wanted to find itself in a situation in which it had to choose between the US and France. This principle was affirmed after 1949 by all governing coalitions and cabinets, and it continued to hold true when reunified Germany regained sovereignty in 1990. But now the scales seem to be tipping clearly in one direction — in favor of France.

<div class="opinary-widget-embed" data-poll="do-you-think-the-new-francogerman-friend" data-customer="deutschewelleeng"></div> <script async type="text/javascript" src="//widgets.opinary.com/embed.js"></script>

Recalibrating alliances

This was not a conscious decision, at least as far as the Berlin side was concerned. But the global order has shifted dramatically in the past two years. Although trans-Atlanticism is not yet in ruins, it is, thanks to Donald Trump, in acute danger of collapsing. As the US uses less and less political capital to cultivate alliances, its disappointed partners are becoming increasingly alienated, and alliances are starting to be recalibrated.

Read more: Can the trans-Atlantic relationship survive Donald Trump?

The Elysee Treaty, now being renewed in Aachen, was essentially a reconciliation treaty between countries that had waged three devastating wars against each other within 75 years. The Germans had hastily added a preamble to the treaty acknowledging the importance of trans-Atlantic relations. The Treaty of Aachen being signed today makes no such references. It dutifully affirms what has been achieved, but it uses an unusually large number of paragraphs to outline forums for joint political action. For instance, military cooperation projects, international fields of action and institutions such as the UN Security Council.

The wording in Article 4 of the new treaty is somewhat cryptic. In it, the Germans and French affirm NATO's promise of military support, which would be completely unnecessary if it could be taken for granted. But since the current US president has been toying with the idea of his country's withdrawal from the military alliance, all the alliance's political certainties have been put to the test.

A matter close to France's heart

The Germans and the French stated that they increasingly draw closer in their defense policy objectives and strategies. Small circles in Paris and Berlin have long been considering if and how France could contribute its nuclear potential to the Franco-German partnership. It is not easy for Germans to negotiate such strategic lines of thought.

Read more: European NATO allies muted on nuclear treaty's demise

On the French side, however, what is now taking place in Aachen is a matter close to the heart. Never before in French history has there been a government so fixated on partnership with Germany. The European Union will break down if President Emmanuel Macron is defeated and the Franco-German project fails. Then left-wing populist Jean-Luc Melenchon and right-wing extremist Marine Le Pen, both of whom are decidedly anti-German and nationalistic, would have good prospects for the French presidency.

The politically battered German chancellor has waited a long time to respond to Macron's European policy initiative, which caused some frustration in Paris. Angela Merkel is now responding with the Treaty of Aachen. If this treaty is put into action, the Germans and French will be taking a giant step forward for European politics. It would be like a second political spring. Why shouldn't Berlin and Paris succeed in doing what is granted many an aging couple?