It stretched over 100 km from Almenara to Santa Cruz de Moya. It consisted of a vast and intricate staggered network of trenches, underground shelters and bunkers capable of withstanding bombs of up to 500 kg. The defensive strategy that best suited the conditions of the rugged Valencian terrain was that of "centres of resistance", with fortified positions supported by the advantage given by the steep terrain and integrated into a line of defense in depth , does not continue.
During its passage through the municipal area of Soneja, this defensive line of the republican rear guard was located in the Altos de Palomera, at the northernmost end of the municipal area. Today, numerous defensive elements are preserved, such as trenches, parapets, shelters, marksman's stands and machine gun nests, spread over a length of about 5 km.

Information taken from the brochure "The XYZ Line in the Alt de Palomera trenches" and Rodríguez and Rodríguez, M.-À. (2019). "Soneja 1936-1939: war rear, post-war concentration camp (Part I)". Bulletin of the Institute of Culture Alt Palancia, 25, p. 149-180. Segorbe (Castelló): Institute of Culture Alt Palancia. Available at the Soneja Municipal Library