The geography of German East Africa also was a severe impediment to British and allied forces. The coastline offered few suitable points for landing and was backed by unhealthy swamps. The line of lakes and mountains to the west proved to be impenetrable. Belgian forces from the Belgian Congo had to be moved through Uganda. On the south, the Ruvuma River was fordable only its upper reaches. In the north, only one practicable pass about five miles wide existed between the Pare Mountains and Mount Kilimanjaro, and here the German forces had been digging in for eighteen months.