BOSTON – Senator Kerry of Massachusetts accepted the Democratic nomination

for president last night in an energetic and relentlessly upbeat

speech that sought to underscore

his toughness and military

prowess.

“I’m John Kerry and I’m reporting for duty,” the 60-year-old senator said as he opened his remarks, prompting prolonged cheers from thousands of delegates and dignitaries at the party’s quadrennial convention.

Invoking his service as a riverboat captain in the Vietnam War, Mr. Kerry vowed that his election would bring no letup in the war against Al Qaeda.

“I defended this country as a young man and I will defend it as president. Let there be no mistake: I will never hesitate to use force when it is required. Any attack will be met with a swift and certain response. I will never give any nation or international institution a veto over our national security and I will build a stronger American military,” the senator said.

In fact, Mr. Kerry promised to intensify the fight against Islamic extremists by restoring support for America and American ideals.

“As president, I will fight a smarter, more effective war on terror. We will deploy every tool in our arsenal, our economic as well as our military might, our principles as well as our firepower,” Mr. Kerry said. “In these dangerous days there is a right way and a wrong way to be strong. Strength is more than tough words. After decades of experience in national security, I know the reach of our power and I know the power of our ideals. We need to make America once again a beacon in the world. We need to be looked up to and not just feared.”

Mr. Kerry responded directly to Republicans and other critics who have painted him as indecisive.

“I know there are those who criticize me for seeing complexities – and I do – because some issues just aren’t all that simple,” he said. Mr. Kerry suggested that President Bush’s policies have often been dangerously simplistic and misguided.

“Saying there are weapons of mass destruction in Iraq doesn’t make it so. Saying we can fight a war on the cheap doesn’t make it so. And proclaiming mission accomplished certainly doesn’t make it so,” the senator said, drawing another roar from the crowd

Mr. Kerry also implied that Mr. Bush unnecessarily took the nation to war in Iraq. “As president, I will bring back this nation’s time-honored tradition: the United States of America never goes to war because we want to. We only go to war because we have to,” the senator said.

Mr. Kerry’s 47-minute speech included a direct appeal to Mr. Bush to conduct a positive, unifying campaign.

“I want to address these next words directly to President George W.Bush. In the weeks ahead, let’s be optimists, not just opponents. Let’s build unity in the American family, not angry division. Let’s honor this nation’s diversity; let’s respect one another; and let’s never misuse for political purposes the most precious document in American history, the Constitution of the United States,” the senator said.

Mr. Kerry said the experience of leading a motley crew in Vietnam has given him a special respect for diversity in a common cause.

“No one cared where we went to school. No one cared about our race or our backgrounds. We were literally all in the same boat. We looked out, one for the other – and we still do,” the senator said. “That is the kind of America I will lead as president – an America where we are all in the same boat.”

The senator also sought to defuse perceptions that the Democratic Party is hostile to religion.

“In this campaign, we welcome people of faith. America is not us and them,” Mr. Kerry said, before offering a glimpse of his own religiosity. “I don’t wear my own faith on my sleeve, but faith has given me values and hope to live by, from Vietnam to this day, from Sunday to Sunday.”

However, Mr. Kerry warned that faith-based political appeals can be taken too far.

“I don’t want to claim that God is on our side,” the senator said. “As Abraham Lincoln told us, I want to pray humbly that we are on God’s side.” That line drew what may have been the loudest cheer of the night.

Countering another Republican line of attack, Mr. Kerry said he had displayed independence in the Senate by breaking with his party to support a balanced budget. He also promised tax relief for middle-income Americans.

“You’ve heard a lot of false charges about this in recent months. So let me say straight out what I will do as president: I will cut middle-class taxes,” the senator said.

Mr. Kerry has not proposed a cut in tax rates. He would increase tax credits and deductions for health insurance and college-tuition payments. He would also send $50 billion in federal money to the states to help lower-income families offset state and local taxes.

The senator brushed aside those who have accused him of being downbeat about America. “There is nothing pessimistic about saying we can do better,” Mr. Kerry said. “It is the heart and soul of patriotism.” He listed a series of issues where he said Americans should be better off than they are.

“What does it mean when 25% of the children in Harlem have asthma because of air pollution?” he asked. “America can do better and help is on the way.” Mr. Kerry returned to this refrain several times, with the crowd chanting in unison, “Help is on the way.”

Throughout his campaign, Mr. Kerry has argued that America must wean itself from foreign oil controlled by repressive Middle Eastern regimes. Last night, he singled out the Saudi government for approbation.

“I want an America that relies on its own ingenuity and innovation, not the Saudi royal family,” he said.

Mr. Kerry was introduced by a former senator from Georgia, Max Cleland, who was badly wounded in Vietnam. Many of Mr. Kerry’s surviving crewmates from Vietnam were on the stage when the senator began speaking.

Earlier in the evening one of Mr. Kerry’s former rivals for the nomination, Wesley Clark, a retired Army general, made a forceful argument that Democrats can be trusted on matters of national security. “Anyone who tells you that one political party has a monopoly on the best defense of our nation is committing a fraud on the American people,” General Clark said.

While nearly every speaker paid tribute to Mr. Kerry’s war record, few made mention of his days as an antiwar protester in the early 1970s. A video about Mr. Kerry shown just before he spoke included a short sequence about his anti-war activism. One clip showed a portion of Mr. Kerry’s 1971 testimony before the Senate Foreign Relations Committee.

“These are commanders who have deserted their troops,” Mr. Kerry said, referring to American political leaders who were directing the Vietnam War.

In his speech last night, Mr. Kerry touched only indirectly on his anti-war years. General Clark’s remarks included a brief reference to that aspect of the senator’s biography.

“John Kerry fought a war and I respect him for that, and he came home to fight a peace and I respect him for that, too,” the retired general said.

Senator Biden of Delaware coupled attacks on Mr. Bush with a biblically inspired prophecy of the defeat of Islamic fundamentalism. “We were told we would pay no price for going it alone. That was wrong,” Mr. Biden said.

One of the evening’s lighter moments came as one of Mr. Kerry’s daughters, Alexandra, recounted how Mr. Kerry once performed cardiopulmonary resuscitation on a hamster that had nearly drowned.

“The hamster was never quite the same after that, but he lived,” Ms. Kerry said.