The Next Unthinkable Attack: Growing Risks of a Third Lebanon War

Executive Summary

• Hamas’ October 7 shock attack, and escalating tensions on the Israel-Lebanon border, are forcing Israel to reassess if its frayed deterrence can hold off massive conflict in the north while it undertakes in Gaza what could be its most demanding operation in decades.
• Since at least last year’s Israel-Lebanon maritime boundary deal, Hezbollah has acted increasingly emboldened to escalate militarily what was long thought to be a fairly quiet frontier to Israel’s north, as its leader Hassan Nasrallah leveraged his group’s tightening coordination with other Iranian proxies to gauge and erode what he perceived as weakening Israeli deterrence and declining military readiness.
• Though Hezbollah likely does not want an all-out Third Lebanon War, which would be catastrophic for both sides, it nevertheless is raising the risks of serious escalation through its ongoing, lower-level attacks that seek to exploit Israel’s distraction in Gaza, further erode Israeli deterrence, and potentially gain further victories and concessions.
• Now Israel faces a strategic crossroads in the north, which may be inseparable from the one it faces in the south: can its weakened deterrence hold off Nasrallah, at least while it focuses immediately on Hamas, or has its deterrent collapsed to the point that Hezbollah’s entry into an Israel-Hamas war is a real possibility, absent further Israeli action?
• Israeli preemption is becoming increasingly plausible against Hezbollah. This is driven by several interrelated factors that have become more acute since October 7, namely:
  • Hezbollah’s much more formidable capabilities than Hamas, including its ability to conduct far larger and more lethal rocket, missile, and ground offensives from the very outset of hostilities, gives Israel a strong first-strike incentive to disrupt, blunt, and neutralize these threats before their full weight can be brought to bear;
  • Israel’s newfound urgency to restore deterrence against Iran and its proxies;
  • Fears that escalation in the north could be much harder to control or defuse than in Gaza, given the prohibitive costs of Hezbollah unleashing a first strike of its own; and
  • Concerns that IDF operations in Gaza could undermine its ability to deal with a second-front attack from Hezbollah, and that the risks of triggering such an attack would grow in proportion to the intensity and extensivity of the Gaza operation.
• Building directly on their important and positive steps thus far to bolster Israel’s freedom of action and U.S. force posture in the Middle East, the Biden administration and Congress must proactively expand these efforts, in word and deed, to help prevent or mitigate an even bigger northern conflict which could move very fast and unexpectedly.

Click here to read the brief.

Click here to view a timeline of rising tensions on the Israel-Lebanon border.

Click here to view an infographic of Hezbollah’s rocket and missile arsenals in 2006 vs. today.

Click here to view a chart of peak projectiles per day fired at Israel.