In 2009, at the end of March, U.S. President Obama had been in office for just two months. The euphoria about his election was still palpable. The break with George W. Bush’s politics, with its symbols and rhetoric, couldn’t happen quickly enough. Already, at the end of March, Secretary of State Hillary Clinton declared the end of Bush’s rhetorical battle cry of the “war on terror.”

With the attack on the Boston Marathon, the “war on terror” is now returning. Not politically — Obama remained true to Bush’s predetermined strategy, anyway. The bombs that went off at a public athletic event were the first terror attack in the U.S. since Sept. 11, 2001, when Islamists steered hijacked passenger planes into the twin towers of the World Trade Center and into the Pentagon.

Terror in his own country: This is a new situation for Obama. And even if the number of casualties this time is nowhere near the proportions of 9/11 — then around 3,000 people died — the psychological impact is enormous.

At the same time, whoever lies behind the cowardly attack remains unknown. Along with radical Islamists, extreme forces within the U.S. itself that have declared war on the political system of the country also come into question. The prospect that the terrorists could be acting out of a conviction of defending original American values is probably a far more terrible alternative for American citizens than Islamist, and therefore somehow “foreign,” terrorists.

Although the political climate may have further radicalized since Obama’s election, terror from within is by no means new. Anarchist Ted Kaczynski, who lived as a hermit in the woods for years, sent sixteen letter bombs between 1978 and 1995 that cost three people their lives; 168 people died in the attack on a government building in Oklahoma City in 1995 by extreme right wingers connected to veteran Timothy McVeigh.

Attacks cannot be prevented by stricter entry requirements and data collection about airline passengers. Instead, the sad truth is: In a free society, there is no absolute security against individuals determined to act. The decisive question is: How much freedom are we ready to give up voluntarily for greater security?