Can bilateral relations promote border construction? Evidence from China-Vietnam borders

Population flow, port trade, industrial agglomeration, network expansion, and security infrastructure, all underpinned by geopolitical cooperation, are reflected in the construction space evolution. Border construction expansion has become a central manifestation of the bilateral relationship development between the two countries. Using the GDELT database to develop a “bilateral augmentation-bilateral segmentation” system, this study measured the bilateral relationship between China and Vietnam at both regional and port scales and identified spatial expansion of border construction, revealing how border construction expansion responds to and interacts with bilateral relations. The results revealed that China-Vietnam relations were primarily driven by diplomatic rhetoric and regional cooperation, with the comprehensive index of bilateral relations showing an upward trend despite fluctuations. The mutation points occurred in 1990, 1996, 2000, and 2010, coinciding with major diplomatic events between the two countries. Border construction expansion between China and Vietnam showed notable temporal differences, national disparities and scale effects, reflecting distinct stages in the evolution of bilateral relations. The bilateral relationship can drive the border construction expansion, with a nonlinear response and a threshold effect. The development of bilateral relations effectively facilitated border construction in both countries, reflecting the essence of cross-border cooperation. These findings offer valuable insights into promoting the sustainable development of bilateral relations and high-quality border construction planning.