Shortly after a Hamas assault that produced the deadliest day Israel has suffered in decades, Israel declared war. The full range of specific actions such a war declaration will entail was not immediately clear, but when Prime Minister Benjamin Netanyahu stated that operations against Hamas forces that had entered Israeli territory would be followed by an “offensive formation,” this was interpreted by many as an indication that ground forces would be sent into Gaza. That possibility looks increasingly likely after Netanyahu told President Joe Biden that Israel must go into Gaza—presumably with the mission of destroying Hamas military capability. To conduct a possible ground assault, the Israel Defense Forces (IDF) have called up over three hundred thousand reservists and continue to mobilize a large force in southern Israel.

If Israel is indeed planning an assault by ground forces into Gaza, these forces will confront a range of challenges—some that will match those of other recent urban battles and others that stem from the unique characteristics of the urban terrain and enemy situation in Gaza. But what will they look like, specifically? Both recent cases of urban warfare and Israel’s previous experience in Gaza yield clues.

It is important to note that while the Gaza Strip’s 140 square miles contain multiple highly dense cities—including Gaza City, Deir al-Balah, Khan Yunis, and Rafah—and are home to over two million residents, the area is not “one of the most densely populated territories on Earth,” as some reports have described it. The densest portion of Gaza, Gaza City, holds over nine thousand residents per square kilometer, but this does not even put it in the top fifty most densely populated cities in the world. A series of recent urban battles have been fought in cities with comparable population densities—like Baghdad in 2003, Fallujah 2004, Mosul and Marawi in 2017, and Kyiv and Mariupol in 2022. But as the lessons of these battles make clear, urban warfare need not take place in “one of the most densely populated territories on Earth” for it to present major difficulties for military forces.

Israel does have experience conducting ground operations in Gaza and against Hamas. The last time Israel sent ground forces into Gaza was during the fifty-day-long Operation Protective Edge in 2014. In that operation, Israel—which had mobilized seventy-five thousand reservists for it—conducted a joint air, land, and sea campaign to support three IDF divisions that moved into Gaza.

Based on both previous Israeli operations against Hamas in the urban areas of Gaza and modern urban battles that took place on comparably dense terrain, several specific challenges are likely to present themselves.

Tactical Challenges Awaiting Ground Forces in Gaza

Combat in dense urban terrain is the most complex and difficult type of warfare a military can be directed to conduct because of the unique interaction of challenges—the dense physical terrain, the presence of noncombatants, restraints on the use of force required by laws of war, and the ubiquitous and real-time global attention on the conduct of a battle.

The last time that Israeli forces entered Gaza was in 2014, which means that Hamas and other combatant groups have had nearly a decade to prepare the defense of Gaza’s cities. Here is a list of the most likely challenges the IDF will face:

Rockets. Hamas has a substantial arsenal of rockets and mortars in Gaza. In 2014, the group fired an estimated six thousands rockets—long-, mid-, and short-range—during the fifty-day battle. It fired over 4,500 rockets in just three days beginning with its barrage on Saturday morning. A 2021 report assessed that Hamas had over eight thousand rockets, meaning that even if it has not increased its stockpiles over the past two years, it has thousands at its disposal with which to target assaulting IDF ground forces. In the 2003 battle for Baghdad, an Iraqi short-range missile destroyed the command post of a US Army brigade in the city. The brigade was conducting the now famous second “Thunder Run,” which would prove critical to the success of the entire battle. Yet such a critical strike by a rocket had the potential to change that outcome.

Drones. One challenge that will be markedly more severe than Israel has faced in its past urban warfare experience is the use of a full spectrum of drones—from military grade suicide drones to commercial, off-the-shelf quadcopters modified to drop munitions. Hamas released video of its forces using drones during its recent attack and showing larger drones in its inventory that are similar to Iranian ones used by Russian forces in Ukraine. As a rapidly growing feature of warfare, recent urban battles have incorporated drones more to a much greater degree than anything the IDF has faced before. During the 2022 Battle of Kyiv, for example, Ukrainian forces employed drones to surprise many observers by defeating the Russian military. They used drones ranging from the Turkish Bayraktar TB2 to made-from-scratch quadcopters to strike targets, call for indirect fire, and anticipate the movement of the Russian forces.

Tunnels. Based on intelligence gained during previous operations to combat Gaza’s tunnels,—including the 2021 Operation Guardian of the Wall, during which Israel reportedly destroyed sixty miles of tunnels in Gaza—there are hundreds of tunnels in Gaza. There is likely what amounts to an entire city of tunnels and bunkers under Gaza’s surface. As it did in 2014, Hamas should be expected to use tunnels offensively to maneuver attackers underground, keeping them both hidden and protected, to conduct surprise attacks. The group will also use them defensively to move between fighting positions to avoid IDF firepower and ground forces. In the 2017 Battle of Mosul, ISIS spent two years digging tunnels, which they used to move between buildings and fighting positions. This greatly contributed the fact that it took over one hundred thousand Iraqi security forces nine months and required destroying most of the city to clear it of enemy forces.

Antiarmor attacks. To enter a contested urban environment, military forces must lead with heavily protected engineer vehicles and tanks—and these must be survivable against the antiarmor weapons of urban defenders. In 2014, IDF vehicles faced Hamas firing a wide range of antitank guided missiles, such as Malyutkas, Konkurs, Fagots, and Kornets, as well as direct-fire rocket propelled grenades, including RPG-7s and the modern and capable RPG-29s. Both these types and other, modern versions of man-portable but effective weapons are easy to transport and conceal in the narrow and confined fighting positions of urban terrain. In the 2004 Second Battle of Fallujah, a single US battalion involved in penetrating the enemy defenses lost six M1A2 Abrams tanks (mostly mobility kills) to RPG volley fire. In the 2022 Battle of Mariupol, just a few thousand defenders used Kornets, NLAWs, Javelin, rocket-propelled grenades, and other antitank guided missiles to destroy many Russian vehicles, hold down over twelve thousands Russians soldiers, and ultimately hold their city for over eighty days.

Strongpoints and snipers. Hamas will seek to use a defense relying on close combat, strongpoints (heavy buildings made of concrete and steel and often with basements and tunnels), and snipers. In 2014, Hamas deployed between 2,500 and 3,500 fighters to defend Gaza using rockets, mortars, antitank guided missiles, rocket-propelled grenades, machine guns, and small arms mostly from protected strongpoints. In urban warfare history, a single building as a strongpoint can take days, weeks, or months to clear. In the 1942 Battle of Stalingrad a four-story building, known as Pavlov’s House, took a division of Germans over fifty-eight days to clear. In the more recent 2017 Battle of Marawi, multiple single buildings took the Philippine military days and in some cases weeks to clear. The IDF should expect to face both strongpoints and snipers once again—both of which have historically been major challenges for attacking militaries.

Human shields. It is well known that Hamas uses civilians as human shields. By doing so, the group is effectively engaging in what scholars have called lawfare, using the law of armed conflict and international humanitarian law—specifically their provisions on the protection of noncombatants—to restrict the actions an attacking military force can take in operations. And while Hamas has cynically used Palestinian residents of Gaza for this purpose in the past—establishing weapons caches and rocket firing points in densely populated areas—it is likely that it will also seek to use the 150 noncombatants kidnapped during the initial attacks over the weekend.

Other Challenges

Of course, urban warfare presents challenges that extend well beyond the tactical level. On top of these are several that will challenge Israel’s efforts at the operational and even strategic level.

Casualties. In 2014, the IDF lost sixty-six soldiers. Given the scale of the attacks Hamas has launched in recent days, Israeli objectives are likely to be even more comprehensive than they were nine years ago. As such, a ground operation into Gaza that aims not only to clear portions of dense urban terrain but to destroy Hamas military capability could lead to significant numbers of IDF casualties.

Ammunition. Urban warfare can require four times as much ammunition, or even more, as combat in other environments. To overcome the tactical challenges described above, the IDF will require an abundance of ammunition—not only small arms ammunition, but also interceptors for air defenses across Israel, precision-guided munitions, active protection system rounds on vehicles, rockets, artillery, mortars, tank rounds and much more.

Unknowns. Finally, there is only so much that the IDF’s prior experience and the modern history of urban warfare can illuminate with respect to the challenges a ground force on Gaza will face. There are also many unknows. As an example, one of them is air defense. Hamas has previously claimed to have several types of man-portable air defense systems, such as the SA-7, SA-18, and SA-24. The presence of these and other air defense weapons would pose a significant challenge to Israeli airpower, with serious implications for the ground forces who are dependent on having cover from above.

The Strategic Context: Will and Time

There should be no mistaking the severity of these challenges. But it is important to acknowledge that they will emerge against a backdrop formed by a fundamental reality: war is a contest of wills. That includes the will of individual soldiers to fight, of politicians to continue a military operation, and of populations to support the political decision to continue fighting.

Moreover, will is not static, but changes over time. More specifically, it becomes difficult to maintain will the longer an operation takes. And in urban warfare, time is a critical component. It takes time to minimize harm to noncombatants. And it takes time to plan, prepare, and execute a city attack in a way that maximizes the likelihood of success. Once an urban battle commences, history makes clear that with each passing day, as civilian casualties and collateral damage mount, international pressure to cease fighting increases. In order to fully achieve the objective of destroying Hamas military capability in Gaza, ground forces will require weeks, if not months. This is the unavoidable nature of clearing urban terrain.

Israel is very aware of the political and military challenge of time. It has fought almost every war of its history in a race against time, seeking to achieve its goals before international pressure forces it to stop operations. This is why Israel has developed a number of best practices to maintain legitimacy and reduce collateral damage in urban warfare. These range from messaging civilians to leave combat areas to “roof knocking” (dropping low-yield explosives on top of roofs in targeted areas to give civilians time to leave before an attack commences) to placing legal advisers at tactical commands and directly involving them in targeting processes.

Ultimately, the outcome of any battle in Gaza will be heavily shaped by the combination of these challenges, a complex set of variables that are entirely incalculable in advance. But it will also be determined by how well IDF forces adapt to meet the challenges, and whether they have the time needed to do so.

John Spencer is chair of urban warfare studies at the Modern War Institute, codirector of MWI’s Urban Warfare Project, and host of the Urban Warfare Project Podcast. He served twenty-five years as an infantry soldier, which included two combat tours in Iraq. In June 2022, he and Liam Collins traveled independently to Ukraine to research the defense of Kyiv. He is the author of the book Connected Soldiers: Life, Leadership, and Social Connection in Modern War and coauthor of Understanding Urban Warfare.

The views expressed are those of the author and do not reflect the official position of the United States Military Academy, Department of the Army, or Department of Defense.