Between 1798 and 1970, USA presidents sent troops into imminent hostilities or transferred arms or other war material abroad without congressional authorization, contrary to the constitutional requirement that Congress alone has the right to declare war. Following the Iran-contra scandal in the USA, the independent prosecutor's report demonstrated in 1994 that those involved at the highest levels of government, including the attorney-general and a national security adviser, attempted to conceal their roles and obstruct official investigations. The report drew attention to serious flaws in government systems of accountability which allowed a constitutional crisis to occur. The report concluded that the then president created the conditions which made possible the crimes committed by others in his administration, including the circumvention of congressional bans, and permitted the creation of a false account of the arms sales to be disseminated to the members of Congress and to the American people. It records a pattern of illicit activity from destruction of evidence to perjury to personal graft. The report demonstrated that present political systems of checks and balances are fallible and in urgent need of reform.