After the battle of Plataea, the Athenians brought their wives and children back to the city, which the Persians had again left in ruins. Not only were the temples and the houses burned, but of the city wall scarce a trace was to be found.
Themistocles encouraged the citizens to rebuild the city, and this they did with good will. More beautiful temples, better houses, soon sprang up under the eager hands of the citizens.
The wall they determined to make so strong and so high that they would be able to defend their city against any attack rather than be compelled again to forsake her.
But Sparta was alarmed at her neighbour's industry; she was more than alarmed, she was suspicious and angry. Athens was making herself too strong, the Spartans murmured in ungenerous mood.
The wall had risen but a little way from the ground when the Spartans sent to ask the Athenians not to go on with their work. The reason they gave was a selfish one, for they said, "If the Persians return and take a strongly walled town so near to Peloponnesus, our cities will not be safe." They then promised to offer shelter to the Athenians, should they again be forced to leave their city, but only on condition that they would stop building a wall around Athens. They even asked the Athenians to help them to destroy the walls that already surrounded the other cities of Greece.
The Athenians were in a dilemma. They were determined to finish the wall, yet they dared not anger the Spartans, lest they attacked their city while the wall was still unfinished.
In their perplexity they turned to Themistocles, who had before now saved them by craft when open defiance threatened to ruin them.
Themistocles was not long in solving the difficulty. He said that he would go as an ambassador to Sparta to talk over the matter. Other ambassadors were to follow him only when the walls were nearly complete, and meanwhile men, women and children, all must work day and night, so that the wall might grow apace.
When Themistocles reached Sparta, he at once said to the council that he could do nothing until his fellow ambassadors arrived, and he pretended that he expected them every day.
He refused to attend the council alone, and when the Spartans grumbled, he assured them that the Athenians were not going on with the wall. When they grew impatient he amused them so well by his clever speeches that they forgot for a little while to be angry with him.
But when day after day passed and still the other ambassadors did not come, the Spartans did not hide their suspicion that they were being deceived. When a rumour reached them that the Athenians had never ceased to build the wall, which was now nearly complete, they were angry indeed, and going to Themistocles they demanded that he should tell them the truth.
He still denied that the citizens had been building the wall in his absence, but if they doubted his word, he bade them send ambassadors to Athens, that they might see for themselves whether he was deceiving them or not.
So the Spartans sent ambassadors to Athens, and then Themistocles bade his colleagues join him, for he knew that now both he and they would be safe. The Spartan ambassadors would be hostages for their lives.
The first thing the Spartans saw as they approached Athens was a high, strong wall. Then they knew that they had been deceived, and they sent a messenger to tell their countrymen that Themistocles had played them false.
Themistocles was no coward. He went into the council and boldly told the Spartans that it was true he had deceived them, so that the walls of Athens might be built before they could interfere.
Indignant as the Spartans were and ashamed of their own folly in being deceived by the crafty Athenian, they dared not harm the ambassadors lest their own messengers should not return in safety.
So they sent them away, and Themistocles and his fellows returned in triumph to Athens.
Soon after this the city wall was finished, and Themistocles then urged the people to build another great wall round the Piraeus. When this was done, Athens had the largest and safest harbour in Greece.
The other states now appointed her to be the head of the allied fleet, and no one was more proud of this than Themistocles. For it was he who had first persuaded the Athenians to make themselves into a great sea-power.