ISIS is far smaller than it was at its peak, but it remains a global terrorist network with several thousand fighters spread across different regions as of 2025. At its height around 2014–2015, it controlled territory roughly the size of England in Iraq and Syria and ruled over millions of people; today it no longer holds major territory but operates as an underground insurgency with active affiliates in parts of the Middle East, Africa, and Central/South Asia.

How big was ISIS at its peak?

  • Around 2014–2015, ISIS controlled an estimated 100,000–110,000 square kilometers of territory across Iraq and Syria, comparable to or larger than Britain in land area.
  • The group governed roughly 8–12 million people under its self-declared “caliphate,” running courts, taxation, and security services alongside brutal repression.
  • Estimates of its manpower at the height vary, but some analyses put the figure at 50,000–80,000 fighters, including tens of thousands of foreign volunteers from over 100 countries.

How big is ISIS now (2025)?

  • In Iraq and Syria, the core ISIS organization is assessed to be down to roughly 1,500–3,000 remaining fighters, operating mainly in rural and desert hideouts and staging sporadic attacks.
  • The group has shifted from running a quasi-state to a classic insurgent and terrorist network: small cells, hit‑and‑run attacks, bombings, assassinations, and extortion of local populations.
  • Its propaganda arm still pushes a global narrative online, though tech platforms and governments have significantly reduced its open presence on mainstream social media.

Global branches and affiliates

  • In Africa, ISIS affiliates have grown in some regions:
    • Islamic State Sahel Province (Mali–Burkina Faso–Niger area) is estimated in the low thousands of fighters and has expanded its presence in rural zones.
* ISIS in Somalia (IS-S) is assessed at around 1,000 fighters and functions as an important logistical and financial hub.
  • In South and Central Asia, ISIS-Khorasan (often called IS-K) has several thousand fighters and has carried out high‑profile attacks, including across Afghanistan and neighboring states.
  • Smaller cells or sympathizer networks exist in other regions (e.g., parts of Southeast Asia and Europe), usually focused on low‑tech attacks and online recruitment rather than holding territory.

Why “how big is ISIS” is tricky

  • Size can mean different things:
    • Territory : virtually none now, compared to a large proto-state in 2014–2015.
* **Fighters** : reduced from tens of thousands to a fragmented network of several thousand across all fronts.

* **Support base and influence** : while active militants are far fewer, ISIS’s ideology still circulates in certain extremist online spaces and conflict zones, which keeps the threat alive even without a caliphate.
  • Analysts stress that underestimating the group after territorial defeat has been a recurring mistake; its strategy now relies on waiting out international attention, regenerating networks, and exploiting civil wars and weak governance.

Recent trendlines and latest context

  • Since around 2019, the main trend has been:
    1. Collapse of the physical caliphate in Iraq and Syria.
    2. Reversion to insurgency in those countries, with steadily lower but persistent attack rates.
    3. Parallel growth of some African and Afghan affiliates that exploit local conflicts and security vacuums.
  • As of 2025, many experts describe ISIS as an “enduring but contained” threat: severely degraded compared with its peak, yet still capable of deadly regional attacks and occasional international operations if security lapses occur.

Information gathered from public forums or data available on the internet and portrayed here.