Serving by choice: Motivations and determinants of voluntary military reservism in Spain.

Military reserves are an essential component of any country's defence system. This study analyzes the Spanish model of voluntary reservists, involving over 3,000 citizens who temporarily join the Armed Forces to train and serve in areas related to their expertise. Using a territory-level dataset covering 2020-2024, the article integrates perspectives from rational choice theory, new institutionalism, public service motivation, and gender studies into a multi-layered explanatory framework. Results indicate that economic and institutional variables are systematically associated with regional differences in reservist numbers, while symbolic factors-proxied through online salience-show mixed but suggestive evidence. The analysis also identifies trends within the reservist population, including increasing female participation, aging, and a limited activation rate. Overall, the findings support a multidimensional model of engagement and offer insights for recruitment strategies, gender integration debates, and civil-military relations in democratic societies.