candidate: Black nationalists in Rhodesia and their overseas supporters , prominently the OAU , clamoured for Britain to remove Smith 's government with a military invasion , but Britain dismissed this option because of various logistical issues , the risk of provoking a pre-emptive Rhodesian strike on Zambia , and the psychological problems that were likely to accompany any confrontation between British and Rhodesian troops in what Smith said would be a " fratricidal war " .