According to an old friend who was a sergeant in the paratrooper: a well placed isolated mine can seriously delay your ennemies'progression.
Then, Colonel Leclerc achieve victory over a largely supperior italian garrison at Koufra with only 300 men and a single artillery piece (a 65mm mountain howitzer). He kept moving the gun around firing from several directions, tricking the Italian commander who believed that he was facing several batteries.
May be not a true answer to the first question but you might find this interesting.
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