Dewey's squadron consisted of seven vessels, of which one was a revenue cutter, and two colliers. He was many thousands of miles from the nearest base of supplies and to fail would mean that he would have to surrender. So, on that momentous voyage, he drilled and drilled his men, until their discipline was perfect. On April 30, land was sighted, and precautions were redoubled, since the enemy might be encountered at any moment. Careful search failed to reveal the Spaniards in Subig Bay, and at six o'clock in the evening, Dewey announced to his officers that he had determined to force Manila Bay that night. At nine o'clock the fleet was off the bay, all lights were extinguished save one at the stern of each ship to serve as a guide for the one following, and even that light was carefully screened on both sides so that it could not be seen from the shore. Then the fleet headed for the harbor mouth. What the defenses of the channel were, no one knew. It was reported to be full of torpedoes. But perhaps Dewey remembered Farragut at Mobile Bay. At any rate, he did not hesitate, but kept straight on, and the fleet had almost passed the harbor mouth, before its presence was discovered. Then the shore batteries opened, but without effect, and the entire squadron passed safely into the harbor. Then followed long hours of waiting for the dawn, and at five o'clock came the signal, "Prepare for action," for the Spanish fleet had been sighted at anchor far down the harbor. Fifteen minutes later, the Spaniards opened fire, but Dewey went silently on toward his goal. Suddenly, a short distance away, there was a dull explosion, and a great mass of water and mud sprang into the air. A mine had been exploded; the fleet had entered the mine fields. Now, if ever, it would be blown into eternity, but there was no pause in the progress of that silent line of battle. From the bridge of the Olympia, the most exposed position in the squadron, Dewey watched the progress of his ships. In the conning tower, eagerly awaiting the word to fire, was Captain Gridley. At last, with a final glance at the shore, Dewey bent over the rail. "You may fire when ready, Gridley," he said, quietly. Ready! Surely that was satire on Dewey's part, for just one second later the bridge under his feet leaped like a springboard as the great gun beneath it gave the signal. Scarcely had the shell left the muzzle when an answering roar came from the other ships. The battle had begun, the Spanish ships were riddled with a shower of bursting shells, their crews cut to pieces, and the ships themselves set on fire. The guns of the American squadron roared with clocklike regularity, while the firing from the Spanish ships steadily decreased. Two hours of this work, and the smoke hung so heavy over the water that it was difficult to distinguish the enemy's ships. "What time is it, Rees?" asked Dewey, of his executive officer. "Seven forty-five, sir."