ISIS attacks against Kobane (Ain al-Arab) very significant for several reasons:
First, ISIS wants to expand its control over a larger geography but Kobane in the middle of ISIS dominated areas, stands as a big obstacle in front of this goal. ISIS currently controls Girsespi (Tab Abyad), Jarablus and Raqqah. It desperately wants Kobane to connect the areas under its control and seize the border gate with Turkey as well.
ISIS also wants to cut Kobane from Kurdish Mountain Region which Afrin is the center and Jazira (Hasakah). As of now, moving between three Kurdish Cantons is difficult. If Kobane falls to ISIS, the situation for Kurds will get much worse. Such a development will also demoralize Kurds psychologically, and will provide advantage to pursue its further goals. ISIS does not hesitate to use any means to seize the city that’s why they even cut off the water of the city.
One other factor to remember is that Kobane is the first city in Rojava to be freed from Assad regime. Therefore, it has a special meaning for Kurds in Rojava. Taking control of such an important city will enable Kobane to seize new territories from east and west direction.
Such an ISIS achievement will also be a message for Kurds that ISIS [and its regional supporters] will not allow Kurdish autonomy in Syria.
ISIS Attack on Kobane and Hasakah
In the long run reaching Hasakah is one of major goals of ISIS. But, Hasakah currently controlled by three different forces YPG (in Kurdish side of the city), Assad and opposition. So, it is not that easy for ISIS to control Hasakah, but they certainly want to expand their control in Syria.
Hasakah City is the administrative center of the Hasakah governorate. It is an important road junction near the Turkish and Iraqi borders. It is also an important agricultural region; wheat, rice, cotton etc. It is also close to oil fields in north (Ramalan area). In a way, controlling Hasakah will provide any group an important advantage over the others.
However, given YPG’s superior military capabilities, discipline and large popular support makes it very difficult for ISIS to defeat YPG and control Kobane.