Israel will not leave hostages behind but this challenge is on a scale the country has not faced before

Israel has warned of a long war to defeat Hamas, but it will surely be hoping to achieve its other main objective much faster - the rescue of more than 200 hostages.

Ground troops have pushed into Gaza in what is being described the "second stage" of their offensive against the militant group that controls the Palestinian enclave.

A tank could be seen from the Israeli side of the border on Sunday firing a large white smoke cloud to conceal the presence of an advancing line of foot soldiers.

Artillery rounds thundered overhead, the noise merging with heavy bursts of gunfire.

Israel has not yet said how many military personnel are deployed on the ground. But a top commander described them as among the nation's best.

It could be a sign of a more surgical aim to this phase in the war to take out specific Hamas targets and perhaps also to find and extract the hostages.

Israel-Hamas war latest: 'Intense' battles on the ground in Gaza

Hamas took more than 220 people from inside Israel hostage, including children, the elderly and foreigners, as part of a brutal terrorist attack on 7 October that triggered the war.

A major diplomatic effort has been under way to secure their release but with only four people so far set free.

The diplomatic push involves other countries like the UK and the US whose citizens are among those taken, with Qatar and Egypt playing important mediatory roles.

Yet plans for a military operation to rescue the captives will doubtless also be on the table especially now that Israel has decided to launch its ground offensive into Gaza.

Any such planning will be a closely guarded secret given the sensitive nature of such an operation.

However, speed must be a factor because of the risk inherent with a ground attack.

Israel has a long record of hostage-rescue operations and is known for never leaving any of its captured citizens behind.

But the challenge posed by this crisis is on a scale the country has not faced before.

Read more:
Mother reconnects with daughter trapped in Gaza
People in Gaza asking where they want to be when they die - MP

Prime Minister Benjamin Netanyahu, in a statement to the nation on Saturday as the Israeli military began ground operations inside Gaza, said his heart was "broken" after meeting with the families of some of the men, women and children who were taken captive.

"I reiterated to them: At every stage up to now and at every stage from now, we will exhaust every possibility to bring our brothers and sisters back to their families."