 Clandestine trade with other nations continued , initially at a reduced level ; among other things , Portugal illicitly labelled unsold Rhodesian tobacco as Mozambican product , then sold it on Salisbury 's behalf in Europe and Asia . Through this and a series of similar sanction @-@ busting operations Rhodesia avoided the economic cataclysm predicted by Wilson , and , with the help of South Africa and Portugal , gradually became more self @-@ sufficient . Aiming to directly cut off the main supply lines of oil to Rhodesia , namely the Portuguese Mozambican ports at Beira and Lourenço Marques , Wilson set up the Beira Patrol , a Royal Navy squadron based in the Mozambique Channel , in March 1966 . This blockade was endorsed the following month by UN Security Council Resolution 221 . Too small to cover both Beira and Lourenço Marques , and unable to legally fire on tankers once they were in Portuguese waters , the patrol met with little success , but it endured regardless for nearly a decade . 
