Wars in Avalon are long, protracted affairs that often last many real life years ebbing and flowing as each side advances only to later retreat as their influence and military dominance waxes and wanes. Most of these are centred around conflicts over the spheres of influence (see HELP INFLUENCE),dominion over the towns and villages of Avalon, levying tribute and growing the army and economy as a result. Skirmishes over spheres of influence are frequent and it is common for a village, town or piece of land to change hands many times in the course of just a few Avalon years.
There are times, however, where disagreements and hated enmities between cities cannot be resolved by small-scale skirmish alone. In these circumstances, a city may choose to bring its army to bear in a full scale invasion of another city; potentially encroaching aggressively into their homeland with intent to destroy, plunder and - ultimately - conquer.
How these invasions come about is manifold, but ALWAYS require the breaching of a city's main line of defence - the fortifications. Fortifications can be destroyed either by besieging (see HELP BESIEGING), by globestave erosion (see HELP GLOBESTAVES), by oil-cauldrons (see HELP OILCAULDRONS) or by ethereal oracular strike (no further details are available). Gatehouse fortifications are known to be innately resilient to attack and are generally around ten times more resistant to siege than their village or town counterpart.
The consequences of war are beyond any other activity in Avalon (see HELP CONSEQUENCE) and as such, an invasion is invariably a prolonged affair, often lasting real life weeks (if the aggressor is competent and indeed successful enough) to see through to any conclusion. The devastating potential consequences of war must ensure that NO invasion can be so overwhelmingly easy - nor too quickly achieved - in order to give the victim ample opportunity to respond to the invasive threat and either retreat, surrender or fight back. To that end, as a general rule of thumb it will take at minimum TWENTY FOUR HOURS for an invasion force to breach a city gatehouse of 100,000 fortifications - often much longer if confronted with an opposing force of legionnaires and this will - if nothing else - guarantee an intensive exchange between the two involved powers.
No general is an island and it should be expected that carrying out an invasion will require an enormous effort and commitment to see through - often a banding together of the entire citizenry where all can play a role in the city's success or failure - any budding invader would be wise to ensure both the army and the citizenry are well trained, well fed and well organised before any such attack can be properly countenanced.