Saudi Arabia and Iran have been battling each other for regional hegemony for years.

Hostilities have increased since the Saudis, backed by the United States, baulked at the 2015 nuclear deal which saw Iran give up nuclear weapons in exchange for sanctions relief and ramped up efforts to curb the Islamic Republic's influence in the region.

Now, Lebanese Prime Minister Saad Hariri is suspected of being held against his will in the Saudi capital, Riyadh. Hariri appeared on television on Sunday night for the first time since his abrupt resignation on November 4.

Hariri rejected what he called rumours of his detention in Saudi Arabia and promised a return to Lebanon "very soon" in order to affirm his decision to give up the premiership.

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"Here in the kingdom of Saudi Arabia, I am free," Hariri said on Future TV, a station affiliated with his political party.

But many, including Hariri's own staff and allies in his unity government, fear that Saudi leadership is mandating the prime minister's actions.

Hassan Nasrallah, head of Lebanon's Shia movement and Iran ally, Hezbollah, said the resignation was "forced".

Hariri's abrupt resignation, coupled with reports that he is being held against his will, have led many to question whether Saudi crown prince Mohammed bin Salman is opening a new front against Iranian influence in Lebanon.

Imad Salamey, associate professor of political science and international affairs at the Lebanese American University, told Al Jazeera it is likely that Saudi Arabia will open a new front in Lebanon as it shifts its view of its relationship with the Sunni community in Lebanon.

Saudi Arabia has close ties to Lebanese businessmen and politicians, including the Hariri family.

"Saudis haven't used these connections against Hezbollah in Lebanon, though Crown Prince Mohammed bin Salman may no longer see this arrangement as beneficial," Salamey said.

Bin Salman is "consolidating power", Salamey said, referencing the arrests of Saudi businessmen and royals, which the kingdom refers to as an "anti-corruption" campaign.

"I think this is why we see [Hariri's resignation] at the same time as the arrests in Saudi Arabia", Salamey said.

This power consolidation extends beyond Saudi borders, Salamey explained. Recently, the Saudis have used their military to project power, especially in its proxy conflicts with Iran in Syria, Iraq and Yemen.

Syria

Considering the Saudis' extended involvement and apparent losses in these conflicts - seen as attempts to curb Iranian influence - the decision to engage Iran in Lebanon may not be wise, according to Joshua Landis, head of the Center for Middle East Studies at the University of Oklahoma and expert on Syria.

Landis believes the contest for military supremacy is already over.

"The Iranians have won the war for military strength in Lebanon, Syria and Iraq. There can be little doubt about this," he told Al Jazeera.

The Syrian civil war began in March 2011, after the tumult of the Arab Spring protests that unseated autocratic leaders throughout the region and attempted to topple Syrian President Bashar al-Assad.

Al-Assad cracked down on protesters calling for democracy in 2011, leading to the creation of armed groups and the eruption of violence.The conflict has killed nearly 500,000 people and displaced millions more.

The Saudis have long wanted al-Assad, an Iran-backed leader from a minority religion who rules over a majority Sunni state, to be removed from power. By mid-2015, Assad was close to losing power.

Then, Russia joined the war in September 2015. Along with Hezbollah and Iranian forces, the Russian intervention gave al-Assad a lifeline.

He has increased his control of the war-torn country's territory from roughly a third in 2015 to a majority stake.

Saudi-backed rebel groups have been routed by pro-Assad forces. The chaotic situation and political vacuum in Syria helped the emergence of the Islamic State of Iraq and the Levant (ISIL, also known as ISIS and Daesh). ISILtook control of parts of Syria but has recently suffered major losses, including its de facto capital, Raqqa.

Iraq

ISIL faces a similar story in Iraq. The group once controlled large swaths of northern Iraq, a country that has been occupied by the US since the 2003 invasion which saw former Iraqi leader Saddam Hussein overthrown, tried and executed.

Now, ISIL is on the verge of losing all its territory there. Similar to Syria, Iraqi forces supported by Iran-backed militias and US-backed Kurds, have been largely responsible for defeating the group.

Iranian influence was previously kept out of Iraq by President Hussein, who fought an eight-year war with the Islamic Republic.

Now, some of the most powerful Shia men in Iraq, including PM Haider al-Abadi, are friendly with Iran.

Al-Abadi recently defended the role of the Iran-backed Popular Mobilization fighters, who have been instrumental in defeating ISIL, in a meeting with US Secretary of State Rex Tillerson.

Iraq is one of the few nations allied with both the US and Iran. Tillerson has been attempting to weaken Iranian influence on Iraq.

"Popular Mobilization fighters should be encouraged because they will be the hope of country and the region," al-Abadi said in a statement in October.

The Iraq-Saudi Arabia border is approximately 900km long. The Saudis share a frontier with a pro-Iran government in Iraq, neighboured by a pro-Iran government in Syria.

Iranian influence in Syria and Iraq, two nations close to the kingdom, has "spooked Saudi Arabia", Landis said, leading to a more aggressive policy from Crown Prince bin Salman.

Yemen

The proxy conflict in which Saudi Arabia has taken the most aggressive stance is Yemen.

Found at the southern end of the Arabian peninsula, Yemen shares a roughly 1,800km border with the Saudi kingdom.

Houthi Rebels, a religious group affiliated with the Zaydi sect of Shia Islam, along with forces loyal to former Yemeni President Ali Abdullah Saleh, took control of large parts of the country in 2014.

Since then, a Saudi-led coalition has engaged in an aerial bombing campaign and blockade. The war has killed more than 10,000 people and left over seven million in danger of starvation.

But the Houthis, who have the support of Iran, have maintained control of much of the country, including the capital, Sanaa.

The Houthis took credit for a ballistic missile fired at the Saudi capital of Riyadh on November 5, telling Al Jazeera the "capital cities of countries that continually shell us, targeting innocent civilians, will not be spared from our missiles".

The Saudis claimed the missile was supplied by Iran, saying it constituted a declaration of war.

Lebanon?

"No one save [Salman] believes that Saudi Arabia has an endgame" for a conflict with Hezbollah, Landis said.

Lebanon's government is based on sectarian appointments. The president must be Maronite Christian, the speaker of the parliament a Shia and the prime minister a Sunni.

Landis said "strong-arming" Hariri could divide Lebanon's Sunni community. Similarly, the Christian community is "much weaker" than before Syria's Civil War.

With both groups weakened, Shia Hezbollah is able "to impose itself on Lebanon with greater ease", Landis concluded.

Trita Parsi, president and founder of the National Iranian American Council, a US-based nonprofit that advocates for Iranian-Americans, told Al Jazeera that while sectarian lines have been drawn, the current crisis is more about power than religion.

Parsi pointed to the Saudi-led blockade against Qatar, a Sunni state, and the aforementioned weakening of Lebanese Sunnis through its treatment of Hariri.

"How does Saudi Arabia advance Sunnis by humiliating the Sunnis of Lebanon?" Parsi said.