Halakhah zu Bamidbar 32:17

With the establishment of Medinat Yisrael, the obligation to make aliyah has become magnified in two aspects. First, the barrier and obstacles of the danger to make aliyah have been removed, and [so has] the obstacle of the inability to earn a living in Israel to the extent of suffering to the point of starvation, G-d forbid. With the removal of these barriers, the halachic exemptions that poskim offer from the obligation to move to Israel are eliminated. Second, we can say the current state in which Medinat Yisrael finds itself – that it has now barely ‘gotten out of diapers’ and is surrounded by enemies sworn to its destruction, Heaven forfend – a special obligation devolves to “arm ourselves swiftly” (see Bemidbar 32:17) and quickly move to Israel and come to the aid of the Jewish people from the enemy that attacked them (see Rambam Hilchot Melachim 5:1)….Indeed, all groups that come to Israel, be they organized or not organized, obviously contribute in this effort, either directly or indirectly.