From memory, I think a set of 7 rules and brute force (but the brute force served only to show that the 7 rules were in all circumstances sufficient).
One rule would be enough for either connect4 or chess because any number of rules can be combined into a single rule.
@4763
"it doesn't matter"
++ It does matter. After chess is weakly solved, a human can memorise say 10,000 perfect games corresponding to a certain repertoire. Then that human would have a tremendous advantage over his peers.
It may also turn out possible to summarise the weak solution of chess into a set of say 1000 rules that can be memorised.
Allen has solved Connect Four by brute force,
but Allis independently solved it with a set of 7 rules.