[The following report was issued by IRIN , a service of the UN Office for the Coordination of Humanitarian Affairs, on 15 April 2013.]

This month, tensions have escalated in Gaza following the first Israeli air strikes since a ceasefire was signed in November 2012.

Despite the November ceasefire, which ended eight days of sustained conflict, the past month has seen both rocket fire aimed at Israel by Gazan armed groups and incursions by Israeli tanks into Gazan territory.

Gaza, which has been under a naval and land blockade since 2007, saw these restrictions loosened after the ceasefire. But in recent weeks, in what was called a response to the rocket fire, Israel has four times closed Kerem Shalom crossing - the only crossing for commercial and humanitarian goods from Israel into Gaza - for days at a time. So far in April, the crossing has been closed for seven days and open for six. Israel also halved the distance fisherman are allowed to go out to sea.

Last week, humanitarian coordinator James Rawley said the closures had depleted stocks of essential supplies, including basic foodstuffs and cooking gas, and undermined the livelihoods and rights of many vulnerable Gazan families.

“If these restrictions continue, the effect upon the Gaza population will be serious,” he said in a statement.

In addition, over 2,400 people remain displaced by the November 2012 conflict, and more than 10,000 remain displaced from previous rounds of fighting.

So what are the chances for lasting peace? Much will depend on those holding the guns, rockets, and bombs.

Israel - as well as rights groups - holds Hamas responsible for any rockets fired from its territory. While Hamas has been able to secure consensus with some of the larger, more moderate groups, it has at times struggled to control other armed groups, which have fired rockets three times since the November ceasefire. Many of these groups see Hamas’ willingness to sign ceasefire agreements with Israel as a sign of its weakness and lack of commitment to the cause of resistance. This month, Hamas police reportedly detained members of one armed groups trying to fire rockets at Israel.

IRIN takes a look at those who can make or break the ceasefire.

Israeli Defense Forces

The Israeli Defense Forces (IDF) were created soon after the establishment of the state of Israel in 1948, combining several Jewish pre-state armed groups, such as Haganah, Palmach, Irgun, and Lehi.

According to the Center for Strategic and International Studies, in 2010, Israel’s army had 176,500 active troops, with another 633,000 in the reserves; 3,501 tanks; 6,852 armored personnel carriers and other armored fighting vehicles; 461 combat aircraft; eighty-one attack and armed helicopters; and sixty-seven major combat ships.

The largest recent Israeli army military operation in Gaza began in December 2008 and lasted 23 days. Over 1,400 Palestinians were killed and 5,000 injured, most of them civilians, according to the Palestinian Centre for Human Rights; nine Israelis were killed, three of them civilians.

Over the eight days of hostilities last November, the Israeli army said it attacked more than 1,500 targets in Gaza, including militants, rocket cells and launchers, tunnels and government centres.

During those hostilities, the army said its Iron Dome system, meant to protect populated areas, also intercepted 421 incoming rockets out of 1,506 fired toward Israel, while more than 800 struck Israel and 152 landed in Gaza, according the army website.

At the time, the army’s chief of staff, Lt Gen Benny Gantz, said the operation had accomplished its goal by killing the head of Hamas’ military brigades and several high-level officials, and inflicting damage on their “launching capabilities.”

He said that, despite the ceasefire, the Israeli Army would continue to thwart attempts to smuggle weapons into the Gaza Strip from Iran or Libya.

Ezzedeen Al-Qassam Brigades

Hamas’ military wing, the Ezzedeen Al-Qassam Brigades, dates back to the early 1980s, but they were only officially organized after the establishment of Hamas as a Palestinian political and military movement in 1987. The brigades’ website states they aim to "contribute in the effort of liberating Palestine and restoring the rights of the Palestinian people.”

Estimates of the strength of the brigades range between 10,000 and 20,000 members. Details of its organization and recruitment are kept a secret, the Al-Qassam’s English website states.

During the hostilities last November, the brigades said it carried out 1,573 rocket attacks, including mortars; locally developed M75 rockets; and more advanced Fajr-5 and Grad rockets, which targeted the large population centres of Tel Aviv (for the first time since the Gulf War) and Jerusalem (for the first time ever). Its members also used homemade projectiles, landmines, and anti-tank weapons against Israeli army border patrols.

Hamas significantly increased the number of rockets fired towards Israel after the assassination of its military commander in November.

As soon as the ceasefire was announced, Al-Qassam said: "While this round has ended, the battle with the enemy [Israel] is not finished, because the occupation is still standing and the enemy is still threatening us.” It added that the "Palestinian resistance" will be always ready.

Al-Quds Brigades

Al-Quds Brigades, the military wing of Islamic Jihad, was founded in the early 1980s, following the establishment of the political wing of the Islamic Jihad Movement in the late 1970s. Islamic Jihad is a more radical offshoot of the Muslim Brotherhood; it has on several occasions used violence when Hamas has refrained, and it has broken ceasefires that Hamas has signed onto and respected.

The second most powerful militant group in Gaza, Al-Quds has the stated goal of leading Islamists to restore their "pioneering role in the Palestinian struggle" against the Israeli "occupation of Palestine," according to its website. It has claimed responsibility for several large-scale attacks since the late 1980s, including bombs on Israeli buses and in restaurants and attacks on Israeli tourists.

During the escalation this past November, it said it fired 620 rockets toward Israeli targets, including anti-ship missiles, Grad rockets, the group’s locally made rockets, C8K missiles, and mortars.

In a statement after the ceasefire, Islamic Jihad said: "The battle continues until all of Palestine is liberated,” and that the end of the aggression did not mean the end of the battle. It reiterated that resistance was the only way to confront occupation.

In a new trend, high-level military coordination took place between Hamas and Islamic Jihad during the November escalation, despite their political differences. Islamic Jihad agreed to the ceasefire brokered by Israel and Hamas.

Al-Aqsa Martyrs’ Brigades

Al-Aqsa Martyrs’ Brigades is the military wing of the Fatah movement, the largest faction of the umbrella Palestine Liberation Organization (PLO), which was officially founded in 1965.

Led by former Palestinian leader Yasser Arafat, Fatah and its military wing, formerly known as al-Asifa, engaged in military operations against Israel until the early 1990s, when the PLO - led by Fatah - started peace negotiations with Israel. This led to the establishment of the Palestinian Authority in 1994.

The group returned to armed struggle during the second intifada in 2000, adopting the name al-Aqsa Martyrs’ Brigades. Al-Aqsa includes several groupsthat sometimes work separately.

Though al-Aqsa Martyrs’ Brigades has been less active in Gaza since the split between Hamas and Fatah in 2007, some of its groups said they fired dozens of rockets toward Israeli targets during the November 2012 hostilities.

The Ayman Jouda Brigades, one of the most active al-Aqsa groups, declared that it fired eighty-one rockets toward Israel, and that it would continue its “struggle” against the Israeli occupation until the “liberation of Palestine”.

Faris al-Lil, another armed group affiliated with the al-Aqsa Brigades, claimed responsibility for the rocket fired on 26 February toward the Israeli city of Ashkelon, which, according to the group, was in retaliation for the death of a Palestinian prisoner in an Israeli prison in February.

Nasser Salaheddine Brigades

The Popular Resistance Committees (PRC) were established as a coalition of armed Palestinian groups from several factions in the early days of the second intifada. The group later became a separate faction with a political leadership and a military arm - the Nasser Salaheddine Brigades.

Like other groups, the Nasser Salaheddine Brigades fired dozens of rockets towards Israeli areas and Israeli military bases in November, and said that they carried out these attacks as a struggle against occupation, according to their website.

After the ceasefire, the group re-iterated that "the resistance is our only option until Palestine is liberated. This is our people`s choice.” It added that weapons were a “right” of protection that could not be limited by a ceasefire.

Abu Ali Mustafa Brigades

The Abu Ali Mustafa Brigades belong to the second-strongest PLO faction, the leftist socialist Popular Front for Liberation of Palestine (PFLP). The PFLP was established after the 1967 war and was active in military operations against Israel during the next two decades, including during the first Intifada, which began in 1987.

The group became more active in armed struggle during the second intifada - which gave several armed groups an opportunity to re-organize - especially after Israel’s assassination of PFLP Secretary General Abu Ali Mustafa in 2001. Named after him, the Brigades retaliated that year by assassinating the Israeli right-wing tourism minister Rechavam Ze`evi.

The Abu Ali Mustafa Brigades took part in 2008-2009 conflict, when its members said they fired dozens of rockets and mortar shells toward Israeli targets.

During the November hostilities last year, the group said it fired 245 rockets and mortars toward Israel. In a statement at the time, the Brigades said: "We will stay in the same trench of resistance to continue the struggle in all forms, and to protect our people, until defeating the occupation. The battle is still ongoing with the enemy."

National Resistance Brigades

The Democratic Front for the Liberation of Palestine (DFLP), which holds leftist and socialist ideals, was established in 1969, and its armed groups, which had several names, were active for the next three decades. During the second intifada, the groups reorganized as the National Resistance Brigades and took part in firing rockets and mortars against Israeli areas beyond Gaza’s borders and at Israeli settlements that existed inside Gaza before the 2005 withdrawal.

It continued its activities during the 2008-2009 conflict, when it fired dozens of locally made rockets, Grad rockets, and mortars toward Israeli areas.

The brigades said in a statement, after the November ceasefire was announced, that it had fired 150 rockets and mortars toward Israel during the eight-day conflict, and coordinated with other armed groups during the escalation. The coordination and cooperation between groups, it said, was an important factor in the recent battle.

Salafist groups

There are also a handful of armed Salafist groups in Gaza - including the Jaish al-Islam (Army of Islam) -which together are thought to have hundreds of members. Members of the Salafist group Tawhid wal Jihad (Monotheism and Jihad), which is linked to al-Qaeda, killed pro-Palestinian Italian activist Vittorio Arrigoni after Hamas failed to release their detained leader in 2011.

Their role in the November conflict was not clear, though assumed to be minimal. They have appeared more strongly in recent months, however. For example, one Salafist group, Maglis Shura al-Mujahideen (Combatants’ Consultative Council), twice claimed responsibility for firing rockets despite Hamas’ ceasefire in November.

Human rights organizations, including Human Rights Watch (HRW), criticized the violations against civilians during the latest conflict. HRW said that many militant groups in Gaza - including al-Qassam Brigades, al-Quds Brigades and the Nasser Salaheddine Brigades - have targeted civilians or “sought to justify the attacks by calling them reprisals for Israeli attacks that killed civilians in Gaza.” HRW called on Hamas, as the ruling authority in Gaza, to punish groups that violate international humanitarian law.

In another report, it also criticized Israel for its air strikes and operations in November.

This report does not necessarily reflect the views of the United Nations.