Here is how Human Rights Watch operates: when it comes to foes of the US (like Russia or Syrian regime), they categorize their actions as war crimes based on youtube and tweets of Syrian rebels. But when it comes to war crimes by US or Israel, they urge caution and then they say that an investigation is needed. After they conduct their own investigation, they rule thus: the US (or Saudi regime or Israel), MAY HAVE committed war crimes. Look at this lousy language of a US war crime: "Serious violations of the laws of war can amount to war crimes. These include deliberately targeting civilians or civilian objects (including mosques), knowingly launching indiscriminate or disproportionate attacks resulting in death or injury to civilians, or being criminally reckless in so doing. The US authorities’ failure to understand the most fundamental aspects of the target and pattern of life around the target raises the question whether officers were criminally reckless in authorizing the attack."