# Entropy signatures of interstate aggression on social cohesion dynamics

## TL;DR

This study uses entropy metrics to analyze how different phases of war affect social cohesion in Ukraine from 2004 to 2025.

## Contribution

The paper introduces a novel framework using entropy to quantify the impact of interstate aggression on social dynamics.

## Key findings

- Social cohesion entropy decreased during partial invasion compared to peace and full invasion.
- Full-scale invasion and peace showed similar entropy signatures, indicating less disruption.
- The methodology offers a way to monitor societal resilience during major events.

## Abstract

This study proposes a systems approach to explore the entropy signatures of war phases on social cohesion dynamics in Ukraine (2004–2025). Using a psycholinguistic time series of online searches for first-person plural pronouns, we quantified social cohesion complexity using sample entropy and refined composite multiscale entropy (RCMSE). Analyses reveal distinct signatures between war phases over time for both metrics, with, respectively, R2 = 0.57 and R2 = 0.95. Relative to peace and full invasion, social cohesion entropy decreased under partial invasion and displayed more anti-persistent behaviour. While social cohesion was most dysfunctional under partial invasion, entropy signatures of full-scale invasion and peace were relatively close. These results offer insights into the impact of interstate aggression on social cohesion and contribute to a dynamical systems understanding of warfare as a systemic shock. The methodology provides a framework for monitoring and predicting societal resilience in response to significant events.