You're seem remarkably naive to even question whether an advanced, well equipped, experienced and highly trained army with 175,000 regulars and nearly half a million reservists could hold off an invasion from militia numbering in the tens of thousands which is already fighting on several fronts stretched out across Iraq and Syria.
Hezbollah has more fighters to potentially call upon than IS... Hamas has regularly attacked the IDF... neither of them are even close to capable of launching anything other than raids... neither is IS... you don't need to be a general to realise that.
Hezbollah has a fighting strength estimated of around 2000 men at any given time...Hamas significantly less than that, both groups are paramilitary in nature and are politically leaning with military wings...ISIS or Islamic State, ISIL or what they call themselves when then expand again is estimated to have a field strength approaching 100,000 men operating in organised, well armed and highly trained commando structures throughout Iraq and Syria. They do include what you refer to as amateurs, however the same can be said for pretty much any conscripted or national service initiated military force in the world, including Israel. Numbers on their own don't mean too much either, penetration and effectiveness in operations do, the Mujahideen in Afghanistan illustrates that just because you have a well armed, well trained, professional army doesn't mean that you are going to be effective or successful and much of ISIS is made up of battle-hardened fighters from across several global theatres many of whom have been fighting in one war or another for over a decade or longer. Also, do not underestimate the difficulty in fighting against asymmetric tactics particularly across borders which are both fluid and under constant pressure from numerous, militant groups and interests.
For ISIS to confront Israel several other things need to happen first, they need to strengthen and stabilise their grip on Iraq both militarily and politically, they are a long way from doing either...also they need to make significant gains in Syria and create this Caliphate in reality, not idealogically as it currently stands. Then they need to suppress and/or absorb the other Islamic Jihadists occupying and operating throughout the region, Hamas being one of those who ISIS is opposed to. They need to reduce the internal power struggles with their own ranks, bring together the various factions of Al Qaeda under a single unified political and military banner and they need to convince the other Salafist states that they are not a threat to them. Their biggest obstacle is not Israel or even The West, it is their own ideology. By claiming global authority they undermine both legitimate and illegitimate Islamist Governments and Authorities in the region and beyond, even their current allies view IS with suspicion and groups such as Al Qaeda are fractious with some supporting and other outright opposing IS.
Israel will not be unduly worried while IS remains occupied in Iraq and Syria, in fact it is in Israel's interests currently as IS oppose Hamas and influence Hezbollah, particularly in Syria. Which weakens both, which benefits Israel.
However, if (or when) ISIS gain sufficient ascendancy in the region then they will potentially be a far greater threat to Israeli security than any current or historical threat it has faced. Time and events will tell, but it is naive to believe that Israel has the strength of arms to suppress such a threat easily or even effectively...as long as the above mentioned conditions are met.
![[TW]Fox](/data/man-of-honor/2009.png){kind=avatar}
Israel is definitely ethnically cleansing Palestine.
