In his youth, Marenches met many of the Allied leaders of World War I, including Marshal Foch and General Pershing.

In 1939, as Count de Marenches, he joined the cavalry of the army and entered the field of intelligence by informing his relatives and contacts in the US of German activities in France im 1940.

Wounded at the Battle of Monte Cassino, he became aide-de-camp to General Alphonse Juin, the commander of the French forces in Italy (1943 — July 1944).

There, Marenches helped coordinate the US military, the French expeditionary corps, and the eventual successful Allied advance into Rome.

Pompidou was aware that factions in the intelligence services had been circulating defamatory rumours for the last six months of de Gaulle's presidency on his wife and himself.

Other rumours alleged Pompidou's involvement with the film star Alain Delon, whose bodyguard had been found murdered in September 1968.

Some agents had taken the opportunity to smear Pompidou in revenge taking very firm action against some of their colleagues involved in the kidnapping of Ben Barka, the leader of the Moroccan opposition in 1965.

The fact that Marenches had been close to de Gaulle's former comrade-in-arms, Alphonse Juin, may have also played a role in the original choice.

Others noted how he successfully cultivated his contacts in the Middle East, pushed the sales of Dassault Mirage fighters, and helped to establish a relationship with Iraq that persisted.

In Africa, sometimes working with the old Gaullist emissary Jacques Foccart and sometimes behaving as his rival, Marenches strengthened France's traditional strongholds.

After the election of Ronald Reagan to the presidency of the United States, he would have become, according to the American journalist Colley, one of his closest advisers doing business in Afghanistan.

Im Dans le secret des princes, he states he was asked by an American journalist, who was a distant relative, where he could go in the world to write an article on an important geopolitical situation that was almost unknown.