Geoffrey Blainey suggests that a civil war is more likely to draw in foreign governments when one of the domestic factions has strong connections beyond its borders. Shared political beliefs, ethnic identities or other affiliations can lead an outside nation to regard that faction’s fortunes as relevant to its own interests. Such ties may create incentives to provide funding, weapons, diplomatic backing or direct military assistance, increasing the risk that an internal conflict becomes an international one.

The argument highlights how domestic divisions can become part of wider regional or ideological rivalries. External support may strengthen a faction, encourage intervention by rival states or extend the scale and duration of fighting. Blainey identifies a condition that can make internationalisation more likely, rather than an inevitable sequence of events. Geography, security concerns, strategic interests and the costs of intervention also influence whether outside powers become involved in a civil war.