How Long Do Interstate Conflicts Last? Evidence from UCDP/PRIO..

How long do wars between states typically last? Using the UCDP/PRIO Armed Conflict Dataset (ACD) v25.1, we analyzed the durations of interstate conflict episodes from 1946 to 2024. We also split episodes by intensity to see whether high-intensity wars tend to last longer.

This post summarizes the results:

Data and definitions.

• Source: UCDP/PRIO Armed Conflict Dataset (ACD) v25.1.

• Scope: Interstate conflicts only (type_of_conflict = 1), years 1946–2024.

• Unit of analysis: Conflict episodes. We reconstruct episodes per conflict_id by grouping contiguous active years, starting a new episode when:

  • UCDP marks an episode end in the previous year (ep_end), or

  • there is a gap of more than one year in activity.

• Duration: For each episode, Duration = end_year − start_year + 1 (in years).

• Intensity classes:

  • High-intensity: the episode contains at least one year with UCDP intensity_level = 2 (≥1000 battle-related deaths in that year).

  • Low-intensity: all years in the episode have intensity_level = 1 (<1000 battle-related deaths per year).

Note: This is a standard and transparent way to turn annual conflict-year panels into episode durations, consistent with the event logic in UCDP.

Key results:

• Overall (all interstate episodes, 1946–2024; N = 21 episodes)

  • Mean duration: about 5.6 years

  • Range: 1 to 14 years

  • Interquartile range (IQR): 7 years

• By intensity

  • High-intensity (≥1000 battle deaths in at least one year of the episode)

    • N = 7 episodes

    • Mean duration ≈ 8.4 years

    • Median duration = 9 years

  • Low-intensity (<1000/year)

    • N = 14 episodes

    • Mean duration ≈ 4.1 years

    • Median duration = 4 years

  Interpretation: High-intensity interstate episodes last notably longer on average than low-intensity ones. The median difference is striking: 9 years versus 4 years.

What the graphic shows:

We created a compact two-panel figure:

Left panel: bar chart of mean episode duration (overall and by intensity).

Right panel: boxplot showing the distribution of durations by intensity class.