The US Army said on Wednesday it was investigating two soldiers who appeared in uniform behind delegates in a video shown during the virtual Democratic National Convention.The appearance renewed questions about the politicization of the military in the run up to November's presidential election. During Tuesday's virtual roll call, each state and territory used a background that was symbolically important to them. The two delegates from American Samoa - which has the highest rate of military enlistment in the United States - appeared in front of two US Army reservist soldiers in uniform."Wearing a uniform to a partisan political event like this is prohibited," the Army said in a statement."The Army follows the Department of Defense's longstanding and well-defined policy regarding political campaigns and elections to avoid the perception of DoD sponsorship, approval or endorsement of any political candidate, campaign or cause," it added.Xochitl Hinojosa, a spokeswoman for the Democratic National Committee, said the appearance was an "oversight."There has been increasing concern about the politicization of the military by President Donald Trump.Those concerns came to a head in the past month after Trump threatened to deploy active duty troops to quell civil unrest in US cities during protests about racism and police brutality.Democratic presidential candidate Joe Biden has also invoked the military in the campaign, saying in June that he worries Trump will try to "steal" the November election but he is confident soldiers would escort Trump from the White House if he loses and does not recognize the result.