[6] There was opposition from Nazi officials to his proposed appointment, in 1941, as professor of law at the University of Frankfurt, but the academics pushed through his candidacy, and he soon advanced to become dean of the faculty.

Turning down an offer from Ludwig Erhard to be deputy minister at the Bavarian Ministry of Economics,[10] he became a professor at Frankfurt University on 1 February 1946, and in April he was elected its rector, a position he retained until 1948.

[24][26] Against the background of the Second World War, a conflict that had caused massive destruction and left the continent split in two by the Iron Curtain, there were calls for increased cooperation in Europe.

[24] Jean Monnet, the leader of the French delegation, and Hallstein drew up the Schuman Plan, which was the basis for the European Coal and Steel Community (ECSC), established by the Treaty of Paris in 1951.

In August 1950, to general surprise, Hallstein was made head of the Office of Foreign Affairs (Dienststelle für auswärtige Angelegenheiten) at the Federal Chancellery (Kanzleramt).

[40] After the ratification of the Paris Accords on 5 May 1955, the General Treaty (Deutschlandvertrag), which largely restored (West) German[j] sovereignty, took full effect; the Federal Republic of Germany became a member of NATO.

[41] There was criticism of a lack of information and consultation and an atmosphere of secrecy, possibly resulting from Adenauer's distrust of the old hands at the Foreign Office, the Wilhelmstraße veterans, as well as the desire to fill top jobs with outsiders not tainted by having served as diplomats under the Nazis.

[42] There were suggestions of a disconnect between the leadership (consisting of Adenauer and a small group of close advisers, including Hallstein and Blankenhorn) on the one hand and the division leaders at the Foreign Office and the diplomatic missions on the other.

In particular, Hallstein was also criticised in the press after the European Defence Community was rejected by the French National Assembly, as had been predicted by the German diplomatic mission in Paris.

[52] Grewe himself writes that he did devise the broad outlines of the policy, but mainly as one of a number of options, the decisions being made by the foreign minister, Brentano, and the chancellor, Adenauer; in any case, the name Hallstein doctrine may have been something of a misnomer.

[59] On 6 September 1955, shortly before Adenauer's trip to Moscow, Hallstein, standing in for Brentano, attended the Noordwijk Conference of foreign ministers convened to evaluate progress made by the Spaak Committee.

[61] In July 1956, Britain made proposals for the Organisation for European Economic Co-operation (OEEC) to examine the possibility of a free trade area for industrial goods.

Hallstein opposed the idea of a wider free trade area at this time, advocating first achieving a greater degree of integration among a smaller number of countries.

[77] Discussions on the possibility of a wider trade area, avoiding the tariff wall between the EEC and the EFTA countries, continued, but in the middle of preparations for the negotiations the French government, on instructions from de Gaulle, withdrew.

[78] On 3 March 1960, Hallstein announced a plan for accelerating the implementation of the common market, which commentators regarded as sabotaging hopes of a joint free trade area that included the EEC and EFTA.

[79] In 1961 Harold Macmillan, the British Prime Minister, finally gave up the idea of the larger free trade area, and the United Kingdom applied to join the EEC.

[87] From the beginning, Hallstein did not believe that de Gaulle's approach of cooperation between sovereign nation states would be able to realize his vision of a powerful Europe that could play its proper part on the world stage.

[86] De Gaulle also envisaged a pooling of sovereignty in certain areas, such as external defence, harmonization of industrial production and foreign trade, currency, exploitation of resources in overseas territories, and cultural and scientific development,[88] but at the same time he was developing the French nuclear deterrent capability, the Force de Frappe, which he envisaged as part of a European defence capability independent of the United States.

[75] When the treaty was ratified by West Germany,[j] the German Bundestag unilaterally added a preamble that re-affirmed the commitment to close transatlantic ties, the enlargement of the existing European Communities and attempts to secure Britain's accession.

Since Britain had firmly expressed its unwillingness to support an autonomous European defence independent of America, de Gaulle regarded the treaty as a failure.

[85] Further attempts by de Gaulle at military cooperation with Germany to the exclusion of America were rebuffed by Erhard (now Federal Chancellor) and his foreign minister Gerhard Schröder.

[92] Hallstein had received indications that other countries shared his point of view and decided to risk the confrontation with de Gaulle, interpreting the instructions from the Council broadly, with the support of Dutch Commissioner for Agriculture, Sicco Mansholt.

[94] France rejected the idea of the increased powers for the European Parliament and of the Community having its own independent revenues, insisting that what had been agreed by the Council regarding the financing of the common agricultural policy be implemented by 30 June 1965.

[97] The Committee of Permanent Representatives of the foreign ministers produced a report recommending a compromise by making both the agricultural levies and the customs duties available to be used for Community purposes but not centralizing the process; however, Hallstein refused to broker this deal and suggested employing the common practice of "stopping the clock" until the issue could be resolved.

Participation in many working groups ceased, and the French Permanent Representative to the EU, Jean-Marc Boegner was recalled, together with 18 high-ranking civil servants and diplomats.

[98][99] In an attempt to resolve the situation, Hallstein, together with Marjolin, the (French) vice-president of the Commission, drew up a new plan, continuing the provisional arrangement for agricultural finances until 1 January 1970.

The other five took note of – but did not formally accept – the opinion of the French delegation that for matters of very important national interest, the discussion should continue until a unanimous agreement was reached.

In his memoirs, de Gaulle wrote of Hallstein He was ardently wedded to the thesis of the super-State, and bent all his skilful efforts towards giving the Community the character and appearance of one.

There he sat, surrounded with all the trappings of sovereignty, directing his colleagues, allocating jobs among them, controlling several thousand officials who were appointed, promoted and remunerated at his discretion, receiving the credentials of foreign ambassadors, laying claim to high honours on the occasion of his official visits, concerned above all to further the amalgamation of the Six, believing that the pressure of events would bring about what he envisaged.According to Der Spiegel, de Gaulle's complaints included[116] On the political role of the Commission, Hallstein stated in an interview with Der Spiegel In principle, we have no political competences ... because there is nothing of that nature in the Rome Treaty.

[134] Though Hallstein first pursued the goal of economic integration, he stated that this was not an end in itself but was a means of achieving a political union that "pool[ed] all the appropriate functions of the member-states.