Palestinian Islamic Jihad (PIJ), the second largest terrorist army in Gaza, recently issued a video threat about its willingness to end the three-year truce in place with Israel.

"If the Israeli enemy continues its normal game and plays with the lives of the Palestinian people, we will break the cease-fire," PIJ leader Ramadan Shallah says in the video, according to an Algemeiner report.

The footage is laced with images of gunmen in camouflage, rising out of the ground, moving through tunnels, and watching areas of southern Israel near the Gaza border. It is interspersed with scenes from a rocket factory, and a close up shot appears of a senior Israel Defense Forces (IDF) officer, who is placed in crosshairs, before a bullet is loaded into a rifle.

"Don't try to test the resistance," says the video's last message.

PIJ remains Iran's favored proxy in the Strip as relations between Tehran and Hamas continue to fluctuate.

The Gaza-based Al-Ansar charity, a Palestinian branch of the Iranian Martyrs Foundation, announced May 21 that it would provide financial grants to "families of martyrs" whose relatives were killed between 2002 and 2014.

A parallel Iranian funding channel is in place for families of "martyrs" killed in the 2014 conflict with Israel.

The Al-Ansar charity is "affiliated with PIJ," according to a report released by the Tel Aviv-based Meir Amit Intelligence and Terrorism Information Center (ITIC).

Iran provides PIJ with both "military and financial support," ITIC noted in its report.

"PIJ is the preferred organization for Iran, due to the problematic nature of the relationship between Iran and Hamas," ITIC Director Col. (ret.) Reuven Erlich, told the Investigative Project on Terrorism.

Although Iran continues to fund Hamas's military wing, relations between Shi'ite Tehran and the Sunni Islamist rulers of Gaza have been unstable since 2012, when the two found themselves on opposite sides of the sectarian war raging in Syria.

Thus, Iran does not currently fund Hamas's non-violent operations, including the salaries for tens of thousands of Hamas government employees.

In recent days, a Hamas senior official even took the trouble to flatly deny Arabic media reports that Iran had resumed full-scale funding for his regime, describing the claims as "fake news."

PIJ, which plays no governmental role, has no such issues with Iran, and it continues to enjoy a high level of Iranian financial support.

A snapshot of that support can be seen in the estimated $8.7 million that was transferred from the Iranian Martyrs Foundation to Gaza over the last three years. Not all the money went to families of those killed in conflict with Israel. "We can assume that some of that money also went towards financing groups like PIJ," Erlich said.

The Al-Ansar charity is used by the Iranian Martyrs Foundation "as a pipeline to funnel funds into the Gaza Strip, in indirect support of terrorism. The money also serves to increase Iran's influence among the Palestinian people, and sends a message to the Sunni Arab world, that it is Iran which is supporting the Palestinians in their struggle against Israel," the ITIC report said.

The Al-Ansar charity is fed with cash by a branch of the Iranian Martyrs Foundation in Lebanon. A second branch of the foundation in Lebanon supports Hizballah.

In 2007, the U.S. Department of Treasury designated the Iranian Martyrs Foundation and its branches in Lebanon as sponsors of terrorism. Israel banned the Al-Ansar charity in 2003, but it reestablished itself in Gaza after the Israeli withdrawal in 2005.

The reelection of Iranian President Hassan Rouhani to a second term is unlikely to dent Iranian funding for terror groups like PIJ, as Supreme Leader Khamanei, who is committed to arming and financing jihadists intent on fighting Israel, continues to exercise control over foreign affairs and military policies.

PIJ has around 5,000 members in its armed wing, the Quds Brigades. The organization has its own Gazan rocket production industry, and PIJ possesses the second largest arsenal of projectiles in Gaza, thanks to Iranian manufacturing knowledge. The organization has been working on improvements to its rocket launch systems. It also digs combat tunnels.

PIJ is a quarter of the size of Hamas's 20,000 armed operatives, but that did not stop it from having numerous past run-ins and power struggles with Hamas.

Since the end of the 2014 conflict with Israel, however, Hamas has improved its ability to coordinate and control the other armed factions operating in its territory.

It remains unclear whether the latest PIJ threat to violate the ceasefire represents a warning of a possible split with Hamas's leadership.

"What matters most is the ideological distinction between the PIJ and Hamas," said Ely Karmon, a senior research scholar at the International Institute for Counter-Terrorism in Herzliya.

"While Hamas, [which is] the Palestinian Muslim Brotherhood, has a strategic cooperation with Iran, PIJ has a religious affinity with the Khomeinist doctrine and regime, since their [former] leaders Fathi Shaqaqi and 'Abd al-'Aziz 'Odah, from the inception of their group, acknowledged the importance of the Iranian revolution and its influence," Karmon told the IPT.

"Sheikh Ahmed Yassin, the Hamas leader, wrote nothing on religious matters (and did not write about any other issues either)," Karmon noted. "Shaqaqi wrote 5 books in which he praised the Iranian revolution."

"In this sense, the PIJ is the real proxy of Iran, and not Hamas," he added.

PIJ leaders integrated themselves into the Iranian-Hizballah camp when Israel expelled them to Lebanon in 1988, Karmon noted. Then, PIJ leader Fathi Shaqaqi was assassinated in Malta in 1995, representing a dramatic blow to the organization.

It took his successor, Ramadan Abdullah Shallah, who is still the current leader, five years following Shaqaqi's assassination to build up the group's infrastructure, with the aid of "major Iranian financial and military support," Karmon said.

"Ironically, Shallah, who spent five years at Durham University [in Britain] writing a thesis on Islamic banking in Jordan, was called to lead the PIJ from the U.S., where he taught at the University of South Florida," Karmon added.

When Hamas released a document that represented an update to its policies last month, feigning a softer stance and a willingness to accept a Palestinian state on the 1967 borders, PIJ's response was unequivocal.

"As partners with our Hamas brothers in the struggle for liberation, we feel concerned over the document," said Islamic Jihad's deputy leader, Ziad Al-Nakhala.

"We are opposed to Hamas's acceptance of a state within the 1967 borders and we think this is a concession which damages our aims," Al-Nakhala said, in comments posted on PIJ's website.

Accepting a state on the 1967 borders would "lead to deadlock and can only produce half-solutions," Al-Nakhala added.

Ultimately, the dispute between PIJ and Hamas is one over tactics, not strategy. In light of its acute isolation, Hamas is seeking to rebrand itself somewhat, without any intention of giving up its long-term goal of destroying Israel.

PIJ, enjoying firm Iranian backing, and lacking all of Hamas's dilemmas of sovereignty, rejects the very idea of a rebranding. It insists on openly advertising its jihadist, Iranian-influenced ideology. Hoisted on Iran's shoulders, PIJ prepares for the next round of fighting with Israel.

Yaakov Lappin is a military and strategic affairs correspondent. He also conducts research and analysis for defense think tanks, and is the Israel correspondent for IHS Jane's Defense Weekly. His book, The Virtual Caliphate, explores the online jihadist presence.