With his death, Mr. Issa, who had been among Israel’s most wanted men, became the senior-most Hamas leader to be killed in Gaza since the start of the war. Israeli officials have characterized the strike as a breakthrough in their campaign to wipe out the Hamas leadership in Gaza.

But experts cautioned that his death — which Hamas has still not acknowledged — would not have a devastating effect on the armed group’s leadership structure. Israel has killed Hamas’s political and military leaders in the past, only to see them quickly replaced.

Here is a closer look at Mr. Issa and what his death means for Hamas and its leadership.

What was Mr. Issa’s role in Hamas?

Mr. Issa, who was 58 or 59 at the time of his death, had served since 2012 as a deputy to Mohammed Deif, the elusive leader of the Qassam Brigades, Hamas’s military wing. Mr. Issa assumed the role after the assassination of another top commander, Ahmed al-Jabari.

Mr. Issa served both on Hamas’s military council and in its Gaza political office, overseen by Yahya Sinwar, the group’s highest-ranking official in the enclave. Mr. Issa was described by Palestinian analysts and former Israeli security officials as an important strategist who played a key role as a liaison between Hamas’s military and political leaders.

Salah al-Din al-Awawdeh, a Palestinian analyst close to Hamas, described Mr. Issa’s position in the group as “part of the front rank of the military wing’s leadership.”

Maj. Gen. Tamir Hayman, the former Israeli military intelligence chief, said Mr. Issa was simultaneously Hamas’s “defense minister,” its deputy military commander and its “strategic mind.”

What does his death mean for the group?

Experts described Mr. Issa as an important associate of Mr. Deif and Mr. Sinwar’s, though they said his death did not represent a threat to the group’s survival.

“There’s always a replacement,” Mr. Awawdeh said. “I don’t think the assassination of any member of the military wing will have an effect on its activities.”

Michael Milshtein, a former Israeli military intelligence officer and an expert on Palestinian affairs, said Mr. Issa’s death was a significant blow to the Qassam Brigades, though he conceded it wasn’t “the end of the world” for Hamas.

“He had a lot of experience,” Mr. Milshtein said. “His death is a big loss for Hamas, but it isn’t a loss that will lead to its collapse and it won’t affect it for a long time. In a week or two, they’ll overcome it.”

Mr. Milshtein added that even though Mr. Issa’s opinion was valued at the highest levels of Hamas, the fact he did not directly command fighters meant that his death did not leave a gaping hole in Hamas’s operations.

How has he been described?

Mr. Issa was a lesser-known member of Hamas’s top brass, maintaining a low profile and rarely appearing in public.

Gerhard Conrad, a former German intelligence officer who met Mr. Issa more than a decade ago, described him as a “decisive and quiet” person lacking charisma. “He was not very eloquent, but he knew what to say, and he was straight to the point,” Mr. Conrad said in an interview.

Mr. Conrad said he met Mr. Issa, Mr. al-Jabari and Mahmoud al-Zahar, another senior Hamas official, about 10 times between 2009 and 2011 in Gaza City. The men met as part of an effort to broker a prisoner swap between Israel and Hamas.

“He was the master of the data on the prisoners,” Mr. Conrad said of Mr. Issa. “He had all the names to be negotiated on.”

Mr. Conrad, however, said it was apparent at the time that Mr. Issa was a subordinate to Mr. al-Jabari. “He was a kind of chief of staff,” he said.

Mr. Issa’s prominence grew only after Mr. al-Jabari’s assassination, but he still was keen to stay out of view. Few images of Mr. Issa are in the public domain.

Mr. Awawdeh, the analyst, called Mr. Issa a man who liked to “remain in the shadows” and who seldom granted interviews to the media.

In one of those rare interviews, Mr. Issa spoke in 2021 about his role in the indirect talks that resulted in Israel exchanging more than 1,000 Palestinian prisoners for a single Israeli soldier, Sgt. First Class Gilad Shalit, and his hopes for a future conflict with Israel.

“Even if the resistance in Palestine is monitored by the enemy at all hours, it will surprise the enemy,” he told Al Jazeera at the time.

In a separate interview with a Hamas publication in 2005, Mr. Issa lauded militants who raided Israeli settlements and military bases, calling the actions “heroic” and an “advanced activity.”

What is known about his early life?

Mr. Issa was born in the Bureij area of central Gaza in 1965, but his family hails from what is now the Ashkelon area in Israel.

A Hamas member for decades, he was involved with the militant group’s effort of pursuing Palestinians who were believed to have collaborated with Israel, according to Mr. Awawdeh.

Mr. Issa spent time in prisons operated by both Israel and the Palestinian Authority.

Rear Adm. Daniel Hagari, a spokesman for the Israeli military, has said that Mr. Issa helped plan the Hamas-led Oct. 7 attack. Mr. Issa is also thought to have planned operations aimed at infiltrating Israeli settlements during the second intifada in the 2000s, Mr. Milshtein said.