Operation Northern Shield

The IDF said it had been aware since 2006 that Hezbollah was attempting to build attack tunnels at multiple points along the northern border.[6] Israeli residents near the Lebanese frontier had, at various points, reported hearing underground digging sounds, and Israeli defense officials had repeatedly denied or declined to discuss the existence of cross-border tunnels.[7]

The IDF's recognition of the threat sharpened significantly in 2012, when Hezbollah leader Hassan Nasrallah publicly spoke of an “Operation Conquering the Galilee,” which Israeli accounts associated with an offensive tunnel component.[8] When residents again reported digging sounds in 2013, the military checked the reports but could not locate tunnels crossing into Israel.[6] The following year, after the 2014 Gaza war demonstrated the scale of Hamas's tunnel program, the IDF established a dedicated Northern Command team in October 2014 to develop an understanding of the offensive tunnel threat along the Lebanese border.[8] Border fortification work, including ground drilling, proceeded alongside this analytical effort, and defensive measures began at some border locations in 2015.[8]

From 2015 onward, Israel began constructing a border barrier and developing specialized tunnel-detection technology.[6] By 2016, the IDF had started deploying technological means along the northern border.[7] Chief of Staff Lt. Gen. Gadi Eisenkot said that an intelligence, engineering, and technological effort to track Hezbollah's tunnel project had been underway since late 2014.[9] The IDF separately said it had prepared for the operation for two and a half years under a standing procedure personally led by Eisenkot.[8] The Diplomatic-Security Cabinet approved the operation weeks before it was launched.[9]

Analysts connected the tunnel project to a broader Hezbollah military concept. An INSS analysis described the tunnels as part of Hezbollah's plan for a ground attack known as “Conquering the Galilee,” intended to let cells of Hezbollah's Radwan commando unit infiltrate Israel and temporarily seize a community, an IDF base, or a main road, creating what the analysis called a “victory photo” in the opening phase of a future war.[4] Israeli accounts described a plan combining underground and above-ground infiltration with a heavy barrage against northern Israel.[4][10] Israel had become aware of Hezbollah's broader plan in 2014, and an account citing then-IDF Chief of Staff Gadi Eizenkot described it as a “grandiose plan” involving a surprise underground infiltration during a barrage of fire.[10]

The IDF publicly launched Operation Northern Shield on December 4, 2018.[8] It said tunnels had penetrated Israeli territory and that forces were working on the Israeli side of the frontier.[8] The military said at the outset that the tunnels were not yet operationally ready and did not pose an immediate threat to Israeli civilians, but that the operation was designed to remove the underground threat before it could be used.[8] IDF Spokesperson Ronen Manelis characterized the number of tunnels as classified at launch, describing it only as a “small number,” and confirmed they were unfinished.[6] The IDF expected the operation to last several weeks.[8]

Prime Minister Benjamin Netanyahu said a tunnel had been built under a home in a civilian neighborhood in southern Lebanon, accused Hezbollah of receiving direct Iranian support and funding for the project, and held the Lebanese government accountable for terrorist activity emanating from Lebanese territory.[9] Israel notified the United Nations about Hezbollah's underground infrastructure, including tunnels that had not yet crossed into Israel, asking UNIFIL to investigate and help ensure they were not completed.[11]

Discovery and Neutralization of the Six Tunnels

The IDF revealed the tunnels in a sequence spread across December 2018 and into January 2019. The first tunnel was reported on December 4, located south of Kafr Kila; it was approximately 200 meters long and extended about 40 meters into Israeli territory.[1] A second tunnel, reported on December 8, was found to be booby-trapped along its Israeli route, as was a third announced on December 11.[1] A fourth tunnel, reported on December 15, came from the direction of Ramyeh toward Zar'it and extended several meters into Israeli territory.[1]

Published accounts gave sharply different measurements for what they described as the tunnel near Metulla. The Jewish Virtual Library reported that it ran from beneath a home near a UNIFIL post, took approximately two years to build, was roughly 80 feet underground and 600 feet long, and extended about 130 feet into Israel. It was six feet wide and six feet tall, and Radwan units reportedly intended to use it to infiltrate and cut off Metulla.[6] A contemporaneous JNS report instead said the tunnel breached nearly 200 meters into Israeli territory and gave dimensions of approximately two meters high and two meters wide at a depth of 25 meters.[9]

A fifth tunnel was blown up by the IDF near Ayta al-Shab on December 26, 2018.[1] The IDF detonated it after warning residents of the village over loudspeakers.[12] A Hezbollah statement cited by Ynet claimed that the IDF had used 190 concrete mixers at tunnel sites by that point.[12] The IDF employed a range of neutralization methods, including explosions and filling passages with water, bentonite, and concrete, selected according to the engineering characteristics of each tunnel.[3] The work was led by Northern Command engineering units and the Yahalom unit.[12]

A striking detail emerged during the neutralization process: after concrete was pumped into one tunnel from the Israeli side, it emerged at a concrete-block plant in Kafr Kila, Lebanon. UNIFIL and Lebanese army forces mapped the plant, and the report said UNIFIL confirmed that a tunnel shaft was located inside it.[3]

On January 12, 2019, the IDF announced a sixth tunnel, running from the Lebanese village of Ramyeh toward Zar'it. The IDF described it as the largest and most complex found during the operation: several hundred meters long, extending tens of meters into Israeli territory, and located 55 meters below ground.[1] It was two meters high and one meter wide, equipped with a waste-disposal track, electric and lighting systems, and a circular staircase cut into the rock that enabled an exit inside Israel.[1] The IDF said it was incomplete when neutralized and did not pose an immediate danger to northern Israeli residents.[1] On January 13, the IDF declared that all cross-border attack tunnels had been found and the tunnel threat to northern Israel had been lifted.[6]

The Flagship Tunnel and May 2019 Destruction

The Ramyeh tunnel announced in January was subsequently described as Hezbollah's “flagship tunnel,” although published accounts differed on its precise dimensions. The Times of Israel reported a length of approximately 800 meters and a depth of 55 meters.[13] The Jewish Virtual Library later listed it as 3,280 feet long and 260 feet deep, with 20 flights of stairs and a 250-foot penetration into Israeli territory near Shtula and Zar'it.[6] Maariv reported that its deepest exposed point was 56 meters below ground.[11]

The sources consistently described sophisticated underground infrastructure. The tunnel had electricity and a rail system for moving equipment and waste, while a detailed Maariv account described hard dolomite rock, ventilation, electrical wiring, telephones, a public-address system, and hundreds of stairs, including more than 300 on the Israeli side.[13][11] The IDF assessed that, had the tunnel been completed, an armed force could have emerged and threatened nearby communities including Even Menachem, Zar'it, and Shtula; only a few meters remained before it could reach the surface inside Israel.[11]

The IDF completed a further destruction and sealing phase for the flagship tunnel on May 30, 2019, after months of intelligence and operational study of its route.[11] Sealing materials were injected into the section extending from the border into Lebanon, rendering it unusable.[11] The IDF said that this work denied Hezbollah a central component of its emergency attack plan.[11]

UNIFIL played an active but limited role in verifying the tunnel discoveries. In a mid-December 2018 assessment, UNIFIL said it had confirmed the existence of all four tunnels Israel had announced at that point, following independent technical investigations and site inspections south of the Blue Line.[14] UNIFIL stated that at least two of those tunnels crossed the Blue Line into Israel and constituted violations of United Nations Security Council Resolution 1701, the resolution that ended the 2006 Lebanon war.[14] UNIFIL did not at that stage confirm Israel's allegation that Hezbollah had dug the tunnels, saying that attribution remained under investigation, and it requested urgent follow-up action by Lebanese authorities.[14]

The IDF characterized the cross-border tunnels as a “flagrant violation of Israeli sovereignty” and called their construction a violation of UN Security Council Resolution 1701.[11] IDF Spokesperson Manelis said Israel held the Lebanese government accountable for terrorist activity emanating from Lebanese territory.[11]

The Lebanese government's response to both the Israeli and UN findings was sharply negative. Lebanese officials rejected the IDF's claims about the tunnels and asked for their exact locations and coordinates.[15] Then-Prime Minister Saad al-Hariri criticized Israeli actions as violations of Lebanese sovereignty while avoiding a direct response to the tunnel discoveries.[15] The U.S. State Department's 2019 Lebanon report stated that the Lebanese government took no action to hold Hezbollah accountable for the cross-border tunnels and prevented UNIFIL from fully investigating them by failing to provide access to the relevant areas.[5] The Lebanese government was also reported to have denied UNIFIL access to tunnel entry points.[6]

UNIFIL's verification figures varied across later accounts. One INSS analysis said UNIFIL verified the existence of five tunnels south of the Blue Line and concluded that two crossed it, attributing the inability to verify all six to obstacles and low visibility inside the tunnels.[16] Another reported that UNIFIL verified five tunnels and that three crossed the Blue Line.[17] Both accounts distinguish UNIFIL's verification from the IDF's announcement that it had found six tunnels, and one states that a tunnel had been destroyed before UNIFIL could visit it.[17]

When the IDF announced the end of the tunnel-search effort on January 13, 2019, it also acknowledged that the work was not entirely complete. The army said it was monitoring sites in Lebanon where Hezbollah was digging underground infrastructure that had not yet crossed into Israeli territory, and noted that neutralization of the last-discovered tunnel would be completed in the following days.[13] The IDF stated that its assessment was that no cross-border attack tunnels remained, while also saying it would shift to a continuing defensive effort along the border, with troops and a tunnel-finding laboratory remaining in place and border-wall construction continuing.[13]

The IDF reported that Hezbollah had stopped digging along the northern border during the month after the operation began.[13] A separate account noted that a small number of tunnels near the fence remained on the Lebanese side and had not been destroyed because they were in Lebanese territory.[11]

Hezbollah's public response was defiant. In a January 26, 2019 interview, Nasrallah said that Israel's discovery of the invasion tunnels had not changed Hezbollah's intention to invade the Galilee in a future war.[18] A Jerusalem Center analysis interpreted the discovery as an operational and morale blow because it removed an important element of surprise from a plan developed over several years, while noting that Nasrallah refused to concede a strategic setback publicly.[18]

The operation took place in the context of longstanding Israel-Hezbollah tensions near the Lebanese border and Israeli measures aimed at constraining and deterring Hezbollah while consulting with UNIFIL.[19] The U.S. State Department's 2018 Country Reports on Terrorism placed it amid broader Israeli concerns about Iranian supplies of advanced weapons and technology to Hezbollah and support for infrastructure to produce rockets and missiles.[20]

Israeli analysts assessed Operation Northern Shield as a significant intelligence and military achievement. An INSS interim assessment, written five weeks after the operation began, characterized the effort as an intelligence, operational, and technological achievement, concluding that the tunnels' destruction denied Hezbollah an important tool for surprise infiltration during a ground attack.[21] It also assessed that the operation avoided escalation and strengthened Israeli deterrence to some extent, while cautioning that Hezbollah's broader military buildup and threats remained.[21]

An assessment by Orna Mizrahi captured the intelligence dimension: “once again, the IDF proved its intelligence superiority by discovering the tunnels and covertly tracking their progress over a period of years. Hezbollah, which had planned to surprise Israel, was instead surprised by Israel's action.”[6] The tunnels' exposure had followed years of intelligence surveillance, culminating in the covert tracking of construction progress without alerting Hezbollah to what Israel had detected.[6]

The engineering scale of Hezbollah's tunnels left a deep impression on analysts. A senior IDF officer described most of the tunnels found in the north as “five star tunnels,” adding that they were “of the kind Hamas could only dream about.”[3] The tunnels collectively featured ventilation ducts, electric connections, and telephones, while the most elaborate passage included a rail system and hundreds of stairs descending through solid dolomite rock.[3][11] Hezbollah claimed that the IDF had used 190 concrete mixers during the operation, while a later Globes report said thousands of cubic meters of concrete were injected into the tunnels.[12][2]

The legacy of the operation was also assessed within the broader framework of Israel's confrontation with Iran's regional influence. An INSS analysis situated the tunnel project within Iran's sustained support for Hezbollah's military buildup, describing its neutralization as part of Israel's ongoing campaign against Iranian regional power projection.[4] The U.S. State Department's assessments in its 2018 and 2019 terrorism reports placed the tunnels in the context of an Iran-backed Hezbollah military threat.[20][5]

Analysts also debated what the operation implied about the completeness of the threat's elimination. While the IDF was confident it had found all tunnels crossing into Israeli territory, Globes reported that the six tunnels might have been only part of the network crossing the border fence.[2] The IDF also acknowledged continuing to monitor Lebanese sites where underground digging had not yet crossed the border.[1] The distinction between the January 13 declaration that the search operation was complete and the May 30 destruction work on the most elaborate tunnel reflected continuing engineering activity after the announced end of the main operation.[6][11]

The operation demonstrated that Hezbollah's Radwan unit had invested heavily in an underground offensive capability intended for the opening phase of a future war. INSS described the tunnel project as excavated over several years in preparation for a wide-scale surprise ground offensive, with UNIFIL confirming that at least some tunnels crossed the Blue Line.[17] Even as the IDF declared the immediate threat neutralized, Nasrallah's public statements indicated that Hezbollah had not abandoned its broader strategic ambition to fight a future war inside Israeli territory.[18] The Jerusalem Center for Foreign Affairs argued that the discovery removed the element of surprise from a possible ground assault into Israeli territory and reshaped the strategic calculus on the northern front, while Hezbollah's rockets, missiles, and above-ground military capabilities remained.[22]

Several aspects of Operation Northern Shield remained subjects of dispute or incomplete verification. The most significant was the question of how many tunnels UNIFIL independently confirmed, and how many of those it verified as crossing the Blue Line. UNIFIL's mid-December 2018 assessment confirmed four tunnels' existence and said at least two crossed the Blue Line, while declining at that stage to attribute authorship to Hezbollah.[14] Later INSS accounts reported different figures: one cited five tunnels verified with two crossing the line, while another cited five verified with three crossing.[16][17] The IDF's own count was six cross-border tunnels, a figure exceeding what UNIFIL was able to confirm independently, partly because one tunnel had been destroyed before UNIFIL could inspect it.[17]

The attribution of the tunnels to Hezbollah, their intended offensive purpose, and the attacks they could have enabled were presented as Israeli military assessments and were contested by Lebanese officials, who rejected the IDF's claims and requested precise coordinates.[15] The U.S. State Department later stated that the Lebanese government prevented UNIFIL from fully investigating the tunnels by failing to provide access to relevant areas.[5]

The operation's timeline also raised questions about what was declared complete. The IDF declared the tunnel-search operation finished on January 13, 2019, while saying that neutralization of the last-discovered passage would continue in the following days.[13] The Jewish Virtual Library and Maariv reported that the IDF completed an additional destruction and sealing phase for the longest or flagship tunnel on May 30, 2019.[6][11] The sources do not fully reconcile the stages, so the January declaration is best understood as the end of the main search operation rather than evidence that every follow-on engineering task had ended. The IDF's concurrent acknowledgment that it continued monitoring underground infrastructure that had not crossed into Israel further complicated the picture of a clean endpoint.[13]