buffer state between Sweden and Imperial Russia's successor state, the Soviet Union, which radically changed the strategic value of northern Sweden, put the usefulness of Boden Fortress into question. Only the most basic needs were satisfied during the interwar period; even apparent needs—based on the experiences from the war—such as better air defence and fortifications to halt or temporarily impede attacks by armoured forces were neglected. Thanks to local commanders, construction of new fortifications and improvements to already existing ones were done with the help of garrisoned troops. Engineer companies built new shelters and trenches as training, and the telephone network was improved and completed by the garrisoned telegraph company. This cut the cost drastically as the only expenditure was the needed material. Only a few necessary projects were funded, including an underground headquarters bunker, improvement of the garrison hospital and new training areas. It was not until the increased tension in Europe following Adolf Hitler's rise to power, Benito Mussolini's March on Rome and the outbreak of the Spanish Civil War that focus once again was put on military readiness and prepared fortifications. Improvements were made to fortifications in many parts of Sweden during the last years of the 1930s following the German annexation of Austria and occupation of Czechoslovakia. In Boden, this included building underground storage rooms for ammunition and food, replenishing already existing stocks, increasing protection for other important supply functions—such as the waterworks—as well as further military planning and also preparations for destruction of—for an advancing enemy—important bridges and roads. When the Second World War broke out, only limited resources were allotted to the defence of Northern Sweden, but following the Soviet attack on Finland a few months later and the German Operation Weserübung against Norway and Denmark the next year, major work on improving and extending the defensive lines was commenced. Bunkers, bomb shelters, gun emplacements—particularly for anti-tank guns—were built by the units that had been mobilised and stationed in the vicinity of Boden. The Finnish experiences gained from meeting superior armoured forces during the Winter War were adopted in Sweden, and triple rows of large stones or blocks of reinforced concrete, dragon's teeth, soon formed a continuous line—defended by anti-tank guns in concrete bunkers and machine-gun nests—around the fortress and city. As the war continued and advances in most fields of warfare were made, Boden Fortress was continually improved to meet new or increased