No one. Any Indian soldiers who currently serve the nation is not allowed to associate with any political party.  Actually, to form or join in a political party is a fundamental rights of Indian citizens which is given in Article-19 of Part-3 of Indian Constitution (Right to Association). But it is also given in Article- 33 of Indian Constitution that Parliamen can restrict or abrogate some fundamental rights of the personel of arm forces to maintain discipline. For this reson no Indian Soldiers is apa member of Indian Congress Party.