The southern boundary between German East Africa and Portuguese East Africa was formed by the River Rovuma, which, coming from the high plateau and the mountains to the east of Nyasa, is one of the large African rivers. Except in its highest reaches near Lake Nyasa it is not fordable, and makes an admirable strategic line. However, as Portugal came into the war after most of the German colony had already been occupied by us, this river acquired strategic importance only toward the end of the campaign, and then in a sense adverse to us, as General Van Deventer has found to his cost. After the remnants of the German native forces had been driven across the Rovuma at the beginning of December, 1917, our forces found the swift pursuit across the river a difficult task. We are, however, now operating against the roving bands into which the enemy force has split, and if ever they try to break back to their occupied colony, they will find the line of the Rovuma a very serious barrier.
The search for the German raider Königsberg.
The Königsberg's guns accompany the enemy on land.
The eastern boundary of the colony is the coast-line of the Indian Ocean for almost five hundred miles, with some very beautiful harbors, and it was dominated by our navy from the day that war was declared. The Royal Navy has played a very active part in our African campaigns, and one of the most fascinating episodes of the war was the search for the Königsberg, lost after she had destroyed the Pegasus and done much damage in the Indian Ocean. She was discovered in a most secluded branch of the Rufiji River, and ultimately destroyed by seaplanes and monitors in her impenetrable lair. Yet, though destroyed, she made her voice heard over all that vast country, for her ten big naval guns, each pulled by teams of four hundred stalwart natives, accompanied the enemy armies in all directions, and, with other naval guns and howitzers smuggled into the country, made the enemy in many a fight stronger in heavy artillery than we were.
Extensive enemy fortifications at the mountain gap.
The rainy season worse than imagined.
From a strategic point of view, the northern frontier was the most difficult of all. It passed north of Kilimanjaro, to the west of which is a desert belt. East of this desert belt and Kilimanjaro the enemy colony was protected by an almost impassable mountain system, with a very narrow, swampy, dangerous gap between the Usambara and Pare Mountains, and another gap of about four or five miles between the Pare Mountains and Kilimanjaro. It was impossible to move an army through the first gap; the second gap at the foot of Kilimanjaro was the place where the enemy had located himself early in the war on British territory, and with patience and skill had dug himself in, with very extensive fortifications, surrounded by dense forests and impassable swamps. Here he lay waiting for eighteen months, threatening British East Africa. From here he was driven in March, 1916, and by the end of that month our forces had conquered the whole Kilimanjaro-Meru areas. It was at this stage, and after our initial success, that the rainy season set in; and that is another great feature of German East Africa. I had read much about it, and I had heard more; but the reality far surpassed the worst I had read or heard. For weeks the rain came down ceaselessly, pitilessly, sometimes three inches in twenty-four hours, until all the hollows became rivers, all the low-lying valleys became lakes, the bridges disappeared, and all roads dissolved in mud. All communications came to an end, and even Moses himself in the desert had not such a commissariat situation as faced me.
The enemy's line of retreat.
When in the latter part of May the rains subsided, the advance against the enemy was once more resumed. In order to create the maximum difficulties for our advance, the enemy chose as his line of retreat the great block of mountains which I have referred to as forming the eastern buttress of the great central plateau. For the next three and a half months our forward movement continued with only one short pause until by the middle of September we had reached the great valleys of the Rufiji and the Great Rwaha in the far south, and across the Rwaha we could link up with General Northey at Iringa in the southwest.
Difficulties of transport and supply in advance.