On August 5, 1904, Hammar boarded the hospital ship Hakuai-maru with destination Dalny where they arrive on August 9. From Dalny he travelled to the front at Port Arthur. At four in the morning on August 21 he climbed a mountain in order to witness the big attack on Port Arthur. The attacks had started on August 8 and by the 21 the Battle of 174 Meter Hill raged and the casualties where high. General Nogi called off the attack by August 24 and concentrated on a prolonged siege.