yes, only the kaliph can and must periodically call offensive jihad on infidels, until the whole world is muslim. And the ottoman sultan was also the last kaliph. Obviously, it's not always possible to wage large wars, so he can run small expeditions to capture slaves/loot, etc, or persecute internal non-muslim minorities, to save face following the letter of the law.

as there is no kaliph, smaller governments must defend the muslim territory they are responsible for - permanent peace which permanently yields their territory to non-muslims is not allowed. And they can call for defensive jihads to defend the umma (all muslims), against attacking infidels.

this explains why bin laden always framed his fights as defense against neo-colonialism, cultural influence, or previous invasions - he knows he lacks the authority to wage offensive jihad with no provocation.

and why egypt could make peace but hamas or fatah can not: egypt surrendered the responsability over Gaza to the PLO.

also, why, if Israel gets weak, muslim countries can claim to be defending the umma, and declare war again.

And why previously muslim lands are always remembered first as targets, such as Spain or India.