Even though most war machines do not have bases, units charging a war machine must still attempt to 'close the door' to align to the centre of the war machine's body (as defined in 'The War Machine' above).
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Source: Warhammer Armies Project: Unofficial 9th Edition (v2.2)
Even though most war machines do not have bases, units charging a war machine must still attempt to 'close the door' to align to the centre of the war machine's body (as defined in 'The War Machine' above).