(except casualties and wounded) consisted of 500 men, and in Tarna: 252, 228, and 231 This reality altered daily life and culture in the town. During calm seasons, the soldiers would go down from the port to the town and would be served a liquor nicknamed "parapet jumper" similar to brandy. This also created civil problems due to a large concentration of troops in a small area. The Republican Offensive of May, 1937 Since the start of 1937, the Francoist army prioritized conquering Madrid. The city proved to be well-armed and fortified, making it impossible at the time. Franco decided to change strategy. He redirected his forces to attack the Cantabrian coast, starting with Euskadi. Franco's army began to concentrate its force against the Basque Country, the Republican side attempted an offensive from Tarna and Pajares that forced the enemy to divert forces. Certain factors affected the present war: The Trubia Arms Factory remained in Republican power Russian weapons are unloaded in Santander The area has raw materials, such as steel and coal It is not possible to import weapons or ammunition from France to Asturias The North Front is isolated and surrounded by land The Republican Fleet is in the Mediterranean protecting Soviet shipments and the Cantabrian Sea is almost in the hands of the Francoist navy The Francoists are greater in number, with 160,000 men compared to 120,000 Franco received weapons from Hitler and Mussolini, in greater quantities than their enemy, with 400 artillery against 250, and 60 tanks against 40 Aviation forces between both sides are strongly skewed, with Franco's own 70 planes, 70 Italian planes and 80 German planes, compared to 70 Republican planes Despite the odds, the Republican offensive was well-planned and started successfully, breaking the balance of forces that existed in the San Isidro-Tarna area. The Republicans advanced through the Cofiñal valley, conquering the Sierra de Rebollares and the opposite bank. They reached Puebla de Lillo. In response, the Francoist command sent 50 trucks with two tanks of regulars and other infantry, to block the advance. Immediately, from its base in León, the German Condor Legion, tried to dislodge the Republicans by bombarding their positions, while Franco's artillery did the same from the ground. This combination wore them out for 20 days. According to some sources, on June 9, Franco visited the area to give direct instructions. The Republican army suffered from its lack