Core Viewpoint - The New Fourth Army, during the Anti-Japanese War, expanded its forces and conducted operations against the enemy in southern regions, with a focus on military production and self-sufficiency in weaponry [1][3]. Group 1: Military Organization and Production - The New Fourth Army was organized into seven divisions after 1941, with notable leaders like Su Yu, who was the commander of the first division [1]. - The first division established a military industrial department responsible for producing ammunition and repairing damaged weapons [3][5]. - Initially, the military industrial department had only about thirty workers and faced challenges in production due to a lack of equipment and resources [6][7]. Group 2: Resource Acquisition and Technical Development - The military industrial department utilized its proximity to Shanghai to procure essential machinery and materials through underground channels, including seamless steel pipes and various tools [8][10]. - The department also acquired technical books to enhance the skills of its personnel, which included a group of college graduates [10]. - Despite advancements in technology, the department faced significant challenges in sourcing raw materials, particularly modern explosives for ammunition [12]. Group 3: Unexpected Resource Gains - The situation changed when Japanese mines, which were poorly constructed, began to drift ashore due to broken anchor lines, leading to the discovery of these mines by local authorities [15][17]. - The military industrial department managed to recover over 2,000 kilograms of explosive material from the mines, which could be used to produce over 4,000 mortar shells [18]. - This unexpected acquisition of resources significantly alleviated the department's challenges in ammunition production, showcasing a serendipitous turn of events [19].