(b) By land through the bottleneck of Zinder with possible but limited Axis support from Libya. No independent air landing operation is possible without the use of Axis resources. (iv) Landing from the Sea. Sufficient shipping and naval escorts exist at Dakar. We do not, however, consider that Vichy would remove many of her war ships or a high proportion of her troops from this area owing to the vulnerability of Dakar itself. Reinforcements could however be brought by sea from the north. We consider, however, that Vichy could bring sufficient forces to seize Duala and Libreville from the sea, and climatic conditions would prevent their recapture by de Gaulle forces until the autumn.