LONDON—Britain will deploy hundreds of military personnel to Afghanistan to help British nationals and local translators get out of the country, defense secretary Ben Wallace said on Thursday as the security situation there worsens. The British embassy in Kabul will be moved to a more secure location and will remain manned by only core staff. The deployment of protection forces and logistical support has been triggered by rising violence as Taliban fighters capture cities across Afghanistan after U.S. and allied troops withdrew. “I have authorized the deployment of additional military personnel to support the diplomatic presence in Kabul, assist British nationals to leave the country, and support the relocation of former Afghan staff who risked their lives serving alongside us,” Wallace said in a statement. “It is a long-planned process and it was important with the current situation on the ground in Afghanistan to make the decision to move to …