The primitive system of encrypted messages keeps the Hamas leader alive

Sinwar largely eschews phone calls, text messages and other electronic communications that Israel can track and that have led to the deaths of other militants. Instead, he uses a complex system of couriers, codes and handwritten notes that allows him to direct Hamas operations even while hiding in underground tunnels, Arab ceasefire negotiators say.

The method of communication has angered the Israeli military, which has been trying to track down the architect of the Oct. 7 attack on Israel that killed 1,200 people and sparked the war in Gaza. Killing or capturing Sinwar would be a significant victory for Israel that could bring the 11-month war closer to an end, but even with military control of Gaza, Israeli intelligence has found nothing.

Sinwar has not been seen in public since the war began last fall. Israeli officials believe he is hiding in Gaza.

One insight into how Sinwar works comes from Arab mediators who pass messages back and forth during ceasefire talks between Hamas and Israel, who do not communicate directly with each other.

A typical message from Sinwar is now handwritten and first forwarded to a trusted Hamas member, who then passes it on to a series of couriers, some of whom may be civilians, the intermediaries said. The messages are often encrypted, with different codes for different recipients, circumstances and times, based on a system Sinwar and other inmates developed during their time in Israeli prisons.

The message could then reach an Arab mediator who had entered the Gaza Strip or another Hamas member who could send it by telephone or other means to members of the group, which the United States designates as terrorists, abroad, the mediators said.

Sinwar's methods of communication have become more cautious and complex since Israel succeeded in tracking down and killing his senior compatriots, most notably in the Beirut attack that killed Saleh al-Arouri, Hamas' deputy political leader and co-founder of the group's military wing.

“I'm pretty sure that's one of the main reasons why the Israeli Defense Forces haven't found him,” Michael Milshtein, former head of the Palestinian Affairs Department of Israel's military intelligence, said of the Israel Defense Forces. “He really sticks to all of his basic personal behavior patterns.”

The Israeli military declined to comment. Hamas would not answer questions about Sinwar's communication methods.

Israel's military intelligence has some of the world's most sophisticated capabilities for intercepting electronic communications, often called signals intelligence. Only after Arouri's death did Sinwar switch almost entirely to handwritten notes and oral communication, sometimes circulating voice recordings through a small circle of advisers, Arab intermediaries said.

Arouri's death was followed by numerous other killings of senior Hamas and Hezbollah officials, heightening the sense of vulnerability. In July, Israel launched a massive airstrike that reportedly killed Hamas' top military leader, Mohammed Deif. That same month, Israel also reportedly killed Ismail Haniyeh, then Hamas' political leader, in Tehran and launched an attack on a Beirut apartment building that killed Fuad Shukr, a key Hezbollah leader who had eluded the U.S. for decades. The Hezbollah commander was dispatched to an apartment after receiving a phone call that likely came from someone who had penetrated Hezbollah's internal communications network, the Wall Street Journal reported.

“They know that anyone who uses electronic devices will be discovered,” says Azmi Keshawi, a researcher with the International Crisis Group who has lived in Gaza. So Sinwar has returned to Hamas' old methods, he says.

Sinwar's rudimentary approach to communication dates back to a system that Hamas used in its early years and that the Hamas leader adopted when he was arrested in 1988 and later imprisoned in an Israeli prison, experts on the group say.

Before his imprisonment, Sinwar founded Hamas' internal security police, called Majd, which hunted down suspected collaborators and was active in Israeli prisons. Majd recruited agents in prison called “Sawa'ed” who distributed coded messages from one department to another, according to the book “Son of Hamas,” by a former Hamas agent turned Israeli spy.

The Sawa'ed, a nickname derived from the Arabic word for forearms, wrapped handwritten letters in white bread, rolled them into balls and then left them to dry and harden, the book says. Like baseball players, the agents tossed the balls from one section of the prison to the next, shouting “Mail from the freedom fighters!”

Israel estimates that Sinwar has been planning a major war with Israel for years, including building a vast network of tunnels. Milshtein, the former Israeli intelligence official, said his preparations likely included setting up a communications system that could bypass modern intelligence methods.

The methods are so effective that his persecutors cannot rule out that he is not in Gaza.

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Access to Sinwar is more important now than ever. Although he was long the driving force of Hamas, the group relied on representatives outside Gaza, such as in Qatar, to represent its interests. That changed after the assassination of Haniya in Tehran – an attack attributed to Israel – which prompted the group to officially appoint Sinwar as its chief.

The change of power came just as the United States was stepping up efforts to broker a ceasefire in Gaza to de-escalate regional tensions. The negotiations are complex, with Israeli Prime Minister Benjamin Netanyahu making a series of demands on contentious issues that will be difficult to resolve. U.S. officials are skeptical that Sinwar himself wants to end the fighting.

Sinwar's cautious approach has temporarily delayed negotiations to end the war. According to Palestinian health officials, more than 41,000 Palestinians have now died, but the number of fighters is not given. In the October 7 attacks that sparked the war, Hamas-led fighters took about 250 people hostage. 97 of them are still in Gaza, many of them presumed dead.

At crucial points in the ceasefire talks, Sinwar was unavailable. At other times, he transmitted messages in near real time. Whether communication delays are a negotiating tactic or a reflection of Sinwar's strict protocols is unclear.

Sinwar has managed to communicate quickly when needed. “We extend our deepest condolences to you and your esteemed family and our blessings for your holy sacrifice,” he wrote in a letter to Haniyeh in April after three of his sons were killed in an Israeli airstrike.

According to Arab authorities, this letter reached Haniyeh just hours after the courier deaths.

In June, senior U.S. officials, including CIA Director William Burns, flew to the Middle East to press Israel and Hamas for a ceasefire. Burns held talks in Doha with the prime minister of Qatar and the Egyptian intelligence chief, who then met with Haniyeh to force Hamas officials to agree to a deal under threat of sanctions and arrest.

During that meeting, Sinwar relayed messages in real time, and Hamas refused to agree to a cessation of fighting unless Israel committed in writing to a permanent ceasefire, according to Arab mediators. It is not clear how Sinwar transmitted his orders.

Israel has known for at least a decade that Hamas has set up a landline telephone system in its underground tunnels. A failed Israeli commando operation in 2018 that led to several days of exchanges of fire between Israel and Hamas was an attempt by the Israeli military to tap Hamas's telephone network, according to a later public statement from Hamas. The Israeli military declined to comment on the operation.

At the beginning of the current war, mediators attempted to broker a hostage deal between Israel and Hamas to prevent an Israeli military invasion of Gaza. They sent couriers into Gaza to meet with members of Hamas's armed wing and transmit coded messages.

Sinwar also arranged phone calls with mediators using Hamas landlines in the tunnels, using codes to determine the day and time and pseudonyms in the messages used to initiate the talks, the mediators said. Sinwar at times used the names of people who were with him in prison to conceal his true identity, the mediators said.

Despite his caution, the Hamas leader only needs to make one mistake to give Israel a chance, says Thomas Withington, an electronic warfare expert and research fellow at the London-based think tank Royal United Services Institute.

“The split second you forget discipline,” Withington said, “can mean your death sentence.”

Write to Summer Said at [email protected] and Rory Jones at [email protected]