Would a Hamas strike be a declaration of war between sovereign nations?

It could get real nasty.

..if Hamas has control over its own military. Hope it doesn't happen tho.

This is what i posted elsewhere august last year:

"Gaza and the westbank are looking more and more like the southafrican "homelands" under the apartheid governments: Territories controlled by an minority government and populated with people denied democratic rights or basic rule of law. They are but big prisons for unwanted ethnic groups and serve to keep those groups under total control.

There is a curios aspect of this though: Because of the growing number of arab voters inside the borders of Israel will face a difficult geo/political dilemma: If she cannot create a new influx of settlers, she will have to either change into a arab dominated democracy or morph herself into something quite like the south african apartheid state.
The US would then face the dilemma of either supporting a decay from democracy or to abolish its current involvement with Israel."

But then - well, something else happened:
a) The US lost its own democracy and
b) Ehud Olmert took over the leadership of Israel and now wants a smaller Israel which can be maintained a jewish ruled democracy.

Not a bad solution actually, the Israeli one.

"The triumph of Hamas, which does not recognize Israel's right to exist, makes it more likely that Olmert will rule out negotiations in favor of unilateral steps to draw Israel's final boundaries around an area where a Jewish majority can be sustained. Those borders, as he outlined in a speech last month, would include major settlement blocs in the West Bank, "security zones" in the territories and all of Jerusalem."

"This is not a relinquishing of the Zionist idea," he said at a policy conference in the coastal town of Herzliya. "Rather it is the essential realization of the Zionist goal: ensuring the existence of a Jewish and democratic state in the land of Israel."

Olmert was once a hard-core "Land of Israel" supporter, although by the late '90s, even while in the Likud, he was willing to concede parts of Jerusalem during the Camp David and Taba peace talks. So I think Olmert would be willing to cut a reasonable peace deal with only, say, a 5% annexation and an equivalent land-swap (what was discussed at Taba).

However, with unilateral withdrawal, it's certainly not going to be all the way to the '67 lines. It'll probably be defined by the current path of the wall, although apparently separating some of the Arab neighborhoods of E. Jerusalem is being considered too. That'll be about a 10-12% de facto annexation. Whether they hold onto the Jordan Valley is another question.

So a unilateral withdrawal would not be to the '67 borders. It would look something like this, the current path of the wall:

it would.