After the war, Einthoven was put in charge of Bureau Nationale Veiligheid, which was renamed Binnenlandse Veiligheidsdienst.

On the orders of a Dutch officer the three Germans, who were being held on the Schiekade, a street north of the Rotterdam city center, were shot as spies.

Police commissioner Einthoven managed to trace the two Dutch soldiers and handed them over to the Germans, resulting in two death sentences (later converted to "discipline house").

After the war, Einthoven was put in charge of the Bureau Nationale Veiligheid, which was renamed Binnenlandse Veiligheidsdienst (BVD) in 1946.

Shortly after the war, Einthoven was informed by the counterintelligence department of the British Secret Intelligence Service that Anton van der Waals [nl] was working for them in Germany.

During the war, Van der Waals had been active for the German Sicherheitsdienst and had betrayed a large number of resistance members.