The company, the estate in Niendorf and the title passed in 1913 with the death of John Freiherr v. Berenberg-Gossler to his son and Partner Cornelius. He had the difficult task both of leading the business through two world wars and of organising its rebuilding. The economy initially got going again after 1918, but inflation, which reached its high point in 1923, as well as deflation and the world economic crisis of 1929/30 which followed all led to permanent new and extreme burdens. In the banking sector there was a wave of fusions and business closures.

In 1930 Cornelius sought a partnership with a stronger institute and found it in the friendly Darmstädter and Nationalbank (Danatbank). However when the German banking crisis worsened in 1931, the jeopardised Danatbank was itself integrated into the Dresdner Bank on the instruction of the newly created banking authority. Cornelius succeeded in regaining sole control of his business and maintaining its independence.

Given the political and economic circumstances in which he saw no scope for a traditional bank active in the export trade, he decided in 1932 to withdraw the business from active banking. The company Joh. Berenberg, Gossler & Co. survived the era of national socialist rule as a holding company in which the company’s shareholdings – amongst others in two smaller private banks primarily engaged in the asset management business – were consolidated.

Numerous diary entries demonstrate that Cornelius Freiherr v. Berenberg-Gossler decisively rejected national socialism. Following the annexing of the Sudetenland and of Austria he wrote in 1938: »Better a small and decently led state than such a huge empire which Germany is today, lawless, without integrity and governed by robbers and murderers.« He supported threatened business friends and acquaintances and was able to help some escape. On 3 May 1945, as English troops marched into Hamburg, the 71-year-old wrote in his diary: »Now the task is to deal with the consequences of the war and gradually try to help the children in building their future.«